Wikipedia.

Contrary to popular belief, Coca-Cola Zero is not a new product. The same blend of aspartame and acesulfame potassium along with the Coca-Cola Classic formula has been available for quite some time in many European countries which were never exposed to New Coke. Commonly called Coca-Cola Light or Coca Light in Europe, the Coca-Cola Zero formula is identical that used in foreign countries.

[ Coca-Cola Zero - Wikipedia, the free encyclopedia ]

And, apparently, Nate's drink of choice.