After bariatric surgery, you should avoid soda no matter what. In my opinion, this was probably one of the hardest things to give up. When you spend most of your life being morbidly obese, you become addicted to foods and beverages.
Have you ever tried meditating? If you recently had weight loss surgery, you might want to give it a shot. After bariatric surgery, your brain might be stuck in your old ways. You physically might not be hungry, but you will mentally think you are. Food addiction is a very real thing and it is important that you address the issue head on.