Re: Why does cola cool quicker than beer or water?

If you are still using a keg for the beer, the answer is easy.
The rate of heat transfer will in general be proportional to the surface 
area across which you are transferring the heat.  If you break it up into 
a bunch of smaller cans, there will be more surface area, and things will 
cool faster.  It's the same reason powdery snow will melt faster than a 
block of ice, or that you can stir-fry small pieces of meat faster than 
you can cook a roast.

If you also have the beer in cans, then I can't think of any reason for 
the behavior you describe.  Certainly the rate of cooling can be 
influenced by what is inside the can, but in this case both fluids would 
be at least 95% water, and the other stuff (ethanol, sugar, carbon 
dioxide) does not seem like it should be enough to make much of a 
difference.  And as far as I know the cans themselves would be the same 
(or course if the beer were in bottles, then you'd have the effect of 
slower heat transfer through a layer of glass than a thin layer of 
aluminum).  Another possible factor, if you have two separate coolers, is 
that if the cans are in contact with an ice-water mixture that will give 
more effective heat transfer than totally unmelted ice where the sides of 
the cans would touch ice and air.

That's all the factors I can think of.  If that still doesn't answer your 
question, feel free to resubmit (maybe with more details like whether the 
beer is in cans just like the soda) and maybe they'll send it to somebody 
with different insight (or who drinks more beer than I do).

Allan Harvey
"Don't blame the government for what I say, or vice-versa."