sign, symptom, or diagnosis, it is appropriate to assign both the V code and the code describing the reason for the non-routine test. 18
The difference is in the types of non -nutritive sweeteners used. Diet Coke has aspartame while Coke Zero has a mix of aspartame and acesulfame potassium. The beverages have different levels of sweetness and off tastes (I.e. high levels of aspartame have a metallic taste) as a result.
Coke Zero is sweetened with a combination of aspartame and acesulfame potassium (Ace-K). Coke Zero is the same basic formula as classic Coke while Diet Coke is a different formula completely. Diet Coke is sweetened with aspartame only. There are unsubstantiated theories (at least by Coca Cola) that the unsuccessful release of Coke Two or new Coke was actually the formula for Diet Coke, just sweetened with the classic sugar combination.