My doctor told be that I can't have anything carbonated. The reason I can't is because it can cause nerve damage to your esophagus-The carbonation sits on top of the band and expands the esophagus. I also can't have caffeine because again it sits on top of the band and it can cause stomache ulcers. To me the risks aren't worth having any caffeine of carbonation. Plus it's just not good for weight loss!