Why can we not have caffeine?

You can have caffeine. The only time medically you should avoid it is the first 6 weeks of recovery. In theory, there is concern that it might contribute to poor healing of your stomach but in reality they want you to not drink soda and telling you no caffeine is a good way to accomplish that. After six weeks you can drink caffeine, you can have soda (the diet kind preferably) and you can have drinks with bubbles. Medically none of that will hurt you, although if you want to actually lose weight, avoiding beverages with high calories is a good idea. Also, some people say that they feel burpy with drinks that have bubbles, so that is also contributory. Your digestive system is not a closed system, so if your stomach has a little extra gas from soda, you burp, problem solved. That silly thing people say that your stomach will expand by drinking carbonated beverages is medically inaccurate.

I am 29 months post-op and I drank caffeine from about 6 weeks out until now. I like caffeine and I wasn't giving up diet pepsi. I hit goal at 18 months and have maintained ever since.

Becase too few medical professionals don't realize coffee is not an diuretic. Moderate use doesn't dehydrate you...http://www.abc.net.au/health/talkinghealth/factbuster/stories/2014/02/27/3951831.htm

That said...that satisfying burn in the gut that only comes from a great cup of joe in the morning...yeah that's stomach acid. That's not conducive to healing a stomach that was cut. So give it a month to heal. Respect the sleeve.