I have been craving a carbonated beverage for a while now. I am six weeks out from a gastric sleeve. After Talking with the doctor he said that at first you want to avoid it due to damage to your incision on your stomach. After you are healed though if you want to drink carbonated things like Perrier or san-pelligrino, drinks that are zero calories but carbonated, that it is okay. The issue with Diet soda's is that they are nothing but chemicals and you don't want those type of things in your body. you want to stick to good healthy natural foods. As far as the stretching of the stomach , I was told and have read that is a myth. endoscopy of patients years after surgery show that the stomach is the same size.