Imagine this is the Matrix, sort of. Food supplies are minimal and an
extreme form of rationing is required. (I'm thinking of what they ate
on the neberkanezer)

What I'm looking for is the most simplest meal solution possible that
will allow a human to maintain as much of a normal life as possible.
This includes providing enough nutrition to maintain normal brain
function as well as moving around. As basic as possible.

It can be in the form of either:

A) Some sort of dish eaten three to four times a day (like gruel for instance)
B) A drink
C) An example daily meal plan that can be repeated every day (must be
repeatable daily, no variety)

The aim is to make it as nutritionally sound as possible but just
barely. It must provide all, or as much as possible, of the vitamins
and minerals humans require.

The ingredients to make it must be available in normal stores or from
Chemists/Pharmacies and it shouldn't require any kind of out of the
ordinary cooking or preparation process or anything illegal. You can
use as much ingredients as you need but remember it needs to be as
simple as possible.

It doesn't need to be high in fat, it needs to be nutritionally sound
and not greatly exceed any daily RDA's.

There is no limit to the cost or any restrictions on how it may potentially taste.

Ultimately, what I'm trying to make is, a packaged
meal/drink/whatever, that can be used every day to maintain life to an
acceptable level. If you had to be stuck on a desert island (that had
no food!), you would want to be stuck with a tonne of this, no matter
how bad tasting or unpleasant to eat it is.

If you can make it nicer tasting or more pleasant to eat, please do
so, within reason.

If any clarification is needed, please ask!

The energy drink Boost (or any other milk-based energy drink) 

And a granola bar...

In the 1970's I saw a US military field 'ration bandolier', a strip of
plastic compartments each holding a few items comprising a 'meal'.

I remember one of the rations was a small tin of sardines and a few
boiled sweets. The idea was to provide variety of taste and
nutritional content.

Without joking, canned dog food would keep people going.

I suspect that you are really after just one thing that is dry and
easy to handle.  Personally I would opt for a simple muesli mix, sure
you need water, but unless you have that you are dead anyway.

"Honey is the only food that includes all the substances necessary to
sustain life, including water."
http://www.goldenblossomhoney.com/amazingfacts.html#health