What are some proven (i.e. backed by documented empirical evidence)
practical (e.g. cleaning?) unconventional (i.e. besides drinking) uses
for Coca-Cola (a.k.a. Coke) either as concentrated syrup or combined
with soda water? *Comments* about fun (legal) uses are also welcome
but will not be paid for.

Hello btn-ga,

By “empirical evidence” (i.e. evidence deriving only from experience,
not from theory), I took it you meant documented statements of  people
saying “I use Coca Cola for …. “

There are certainly numerous urban legends out there about highway
patrols using Coke to clean blood off cars, how Coke can dissolve a
nail in two days, etc.  These tend to be mixed with more plausible
hints for cleaning with Coke.  There is a discussion on which of the
allegations are true and which are false at TruthorFiction.com:
http://www.truthorfiction.com/rumors/watervscoke.htm

I think that the best documented uses are in cooking since you
actually get proper recipes, even some endorsed by the Coca Cola
company at http://www2.coca-cola.com/ourcompany/recipes.html
Recipes on the site include:
Banana Cake, Barbequed Ham, Casserole BBQ, Chicken, Chinese Pepper
Steak, Coca Cola Ham, Family Pot Roast, French Onion Soup, Matchless
Meat Loaf, Southern Belle Salad, Steak Fried Onions, Sweet and Sour
Cabbage, Barbeque Sauce, Chocolate Cola Cake, Coconnut Shake,Cola
Cake, Cuba Libre Chiffon Pie, Date Nut Bread, Easy Low Fat Cake and
Gingerbread Deluxe

The book How to Eat (2000) by Nigella Lawson also includes a recipe
for Ham in Coca Cola
www.stylenetwork.com/Shows/Nigella/ Recipes/hamincoke.html

Or you might prefer Minestrone Soup Coca Cola:
http://www.recipesource.com/soups/soups/06/rec0644.html

There are lots of others to be found if you search Google for Coca
Cola + recipes

Coca Cola is also mentioned in a serious support forum. A member of
the PST Tech Support Discussion Forum messaged “We use Coke in the
shop to remove the residue from spilled battery acid inside the
timers. We only use Coke, not diet, not other colas. They just don't
seem to work as well.”
http://cgi.abacom.com/cgi-bin/psttech/forum/forum?read=275
In reply, another participant messaged: “have a Canon Speedlite 177A
flash unit which contained a couple of batteries that had corroded and
oozed into the battery compartment. I found his message and decided to
try using Coke to clean it. Coke did a very good job of cleaning up
the mess in the compartment and on the contacts and getting the
Speedlite usable again.”
http://cgi.abacom.com/cgi-bin/psttech/forum/forum?read=566

Household hints by Susan Doyle at
http://www.kitchenproject.com/susan/Coca_Cola_for_cleaning_stains.htm 
also mentions Coke used as a toilet cleaner, and adds that it can be
used for removing grass and grease stains from clothes: “use your
regular cleaning items, detergent, color safe chlorine bleach, etc.,
in hot water and
ADD ONE 12 OZ. CAN OF COLA to the wash water. Continue on as usual.
Another use for cola, take the greasy film off the windshield. Wet
cloth with cola and wash the window, rinse and dry.”

From http://www.wackyuses.com/author.html
“Joey Green has been called "a modern-day Heloise" by the New York
Times and the "Pantry Professor" by People magazine… … has been seen
polishing furniture with SPAM on CNN Headline News and cleaning a
toilet with Coca-Cola in The New York Times.”

Other uses he lists at: http://www.wackyuses.com/coke.html
Remove rust spots from chrome car bumpers.
Clean corrosion from car battery terminals.
Loosen a rusted bolt.
Bake a moist ham.
Remove grease from clothes.

Uses listed by visitors to his site:
"My son-in-law, who is in the Army, says he uses Baby Wipes to clean
the camouflage off his face while they are out in the field and good
old Coca Cola to clean the carbon off his weapons."

"the cat got on the countertop in the kitchen and knocked over my
Mom's jar of bacon grease onto the linoleum floor… … Mom tried every
kind of soap and detergent to get rid of the stain, but none worked.
Years later, during my brother's birthday party, someone spilled a
Coca Cola on the floor, right over the stain, and it got left there
until the party was over. When that mess got mopped up, the ugly
grease stain had disappeared!"

"Years ago, we were doing a television special from the Ed Sullivan
Theatre in New York City…. …they had polished the stage and the girls
kept slipping. We bought a case of Coke and poured it on the stage
which made it sticky enough to proceed."

Joey has published a series of books on strange uses of common
household products.  These are listed at
http://www.wackyuses.com/books.html and are all available on
Amazon.com
Titles include:
Clean Your Clothes with Cheez Whiz
Polish Your Furniture with Panty Hose
Paint Your House with Powdered Milk
Wash Your Hair with Whipped Cream
Joey Green's Encyclopedia of Brand-Name Products

To add to the list of cleaning uses, my schoolfriend’s brother used it
to clean his coin collection.

I didn’t find any uses listed for the syrup.  

Search strategy: Coca Cola strange uses
://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=Coca+cola+strange+uses
Coca Cola cleaning ://www.google.com/search?q=cleaning+Coca+Cola&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&start=10&sa=N
Recipes Coca Cola ://www.google.com/search?q=recipes+Coca+Cola&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&start=0&sa=N

Fascinating! :) Now this information is in one convenient place on the
Internet thanks to tehuti-ga, the commentators and Google. During my
fleeting curiosity, I only found the truthorfiction.com page along
with many instances of urban legends being spread. I even found a
serious newspaper article citing the urban legends! This service is
awesome. Thanks everyone! BTW, I hope that people continue to comment
with even more Coke uses...

I've used Coke to clean corroded battery terminal posts on my car. 
Any carbonated drink'll do. Sorry that's all I got.

Pwi_Pwii

good for getting bugs off the car body//windsheild too
and I've seen recipes for coca-cola cake, and as a marinade for baked ham

You can find more recipes using Coke at 
http://members.amaonline.com/nrogers/Kitchen/coca_cola.htm

Also, if you search for "Coca-Cola Recipe" you will find the
active ingredients of Coke listed. Most applications for Coke
rely on the acid in the Coke, and these applications could also be performed
with vinegar.

Also, you can use Coke as a hair-wash to get rid of
hair lice. See near the bottom of the Webpage:
http://www.hintsandthings.com/nursery/lice.htm

The story I always used to hear was how people could take a couple
spoonfuls of Coca Cola syrup to calm an upset stomach.  These links
refer to that, though, I can't confirm their validity.
http://www.meridianinstitute.com/echerb/Files/5097-1.html
http://www.mouthshut.com/readreview/6847-1.html

A nice thread about the cola as a cleaner.  And, those who disagree:
http://www.bangladesh.com/forums/showthread.php3?threadid=6274

You may find these sites amusing, as well:
http://www2.coca-cola.com/contactus/myths_rumors/

http://www.snopes.com/cokelore/

And, if you like to mix a little Conspiracy with your Cola, yikes:
http://www.skolnicksreport.com/cocaccc.html

I heard of teenagers using Coke as a suntan lotion, to get a darker tan.

Also, you can add a few "Pop-Rocks" and make yourself a "Kevorkian Fizz." 

( http://www.topsecretrecipes.com/sleuth/legends/legend3.htm )

I've heard (and this came from a reputable source but I can't seem to
find evidence to back it up on the Internet) that in a jiff, Coke can
be used as a spermicide.  Kind of nasty, but hey -- it apparently
works.

Coke was invented by a pharmacist and when you drink just the syrup
(which you can order through Walgreens) it will stop you from
vomiting.

I heard that in Brazil they mix it with olive oil for a dark tan
lotion.

A friend of mine has a building company and they use coke to remove
rust from those steel mats that are used to reinforce concrete.
No kidding - it works.
Maybe itīs the phosporous acid contained in coke that removes the
rust.

till-ga

Dear BTN, 

A Colombian friend of mine used to cook a very good rice with Coke and
raisins. She said its a very popular food in Colombia.

I have a book that teaches how to make home-made persents such as
jams, relishes. In its advices on cleaning your regular supermarket
jars from whatever was in them, and removing the sticker, Coke is
recommended.

There are many things you can do with the plastic bottles, too. For
example, if you cut it into pieces and put it into warm water, you can
make ear-rings or beads of them.

That all, but thanks for asking. I am learning new stuff.

I use flat coke (carbon dioxide removed) for an upset stomach, it is
quite effective in stopping diarrhoea.

The river Trent in Nottingham, England is notorious for causing "Trent
River Belly" (apparently due to Power Stations heating the water
up-stream which allows bugs to flourish) in White Water Kayakers using
the man-made White Water course and ingesting the water.  The
generally accepted cure-all for regular users is an ample intake of
Coke.  Diet Coke, Pepsi or any other type of Cola drinks are not seen
as a substitute for Coke.