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.
Most diet sodas are sweetened with zero-calorie, zero-carbohydrate artificial sweeteners like sucralose and aspartame. Because these sweeteners contain no carbohydrates, they are generally okay for consumption from the standpoint of not interfering with the physiology behind low-carb diets.