is it possible to get a drink in New York city in a public bar or
similar at 0800 in the morning - say a shot of grappa with a coffee or
do licensing regulations prevent this ?

Hi Michael,

Inside the city of New York, the laws of the of New York State apply,
outside the city limits, county laws apply. Since you asked about NYC
proper, here is your answer:

The sale (or giving away) of liquor by licensed premises --for on-site
consumption, is prohibited in NYC between the hours of 4am and 8am
Monday through Saturday, and 4am to 12 noon on Sunday. There are no
exceptions.

Reference:

New York State Consolidated Laws 
Alcoholic Beverage Control
http://caselaw.lp.findlaw.com/nycodes/c5/a9.html

S 106.5. No alcoholic beverages shall be sold, offered for sale or
given away upon any premises licensed to sell alcoholic beverages at
retail for on-premises consumption, during the following hours:

  (a) Sunday, from four ante meridiem to twelve noon.
  (b) On any other day between four ante meridiem and eight ante meridiem.


So, at 8am you may order coffee with Bailey's (for example), but not at 7:55am...


Hope this helps!


~~Cynthia


Search terms:
NYC liquor regulations OR laws

I thought that would be easy to find.
You might ask these people:
http://newyork.citysearch.com/roundup/40095/newyork/24_7_in_new_york.html?