Another major difference between Diet Coke and Coke Zero, Sharp points out, is caffeine content. A 12-ounce can of Diet Coke has about 46 milligrams, while Coke Zero has 34 milligrams.

Even though Sprite does not contain caffeine, it’s loaded with sugar and, ... Coke Zero (Coca-Cola Zero Sugar) is marketed as a healthier version of the original Coca-Cola Classic.