I was given the following reasons to refrain from alcohol: (1) empty calories (2) can contribute to worsening GERD (3) metabolization of the alcohol may have undesired effects with your new digestive system (4) risk of transfer addiction.
I was not told never to have it again, but to use caution before proceeding.
I rarely had alcohol during weight loss phase, I would guess probably less than 10 times the entire time, and these times wouldn't even be an entire regular "serving". It was always dry red wine or gin/vodka with soda (less calories and less carbs). I once had a couple sips of a flavoured soju like 2 months post op and ended up on the bathroom floor for over an hour. Not pretty.
I can get tipsy/drunk reeeaaalllly quickly (and on much, much, much less than pre-op). But I also sober up astonishingly quickly as well. 1 drink and I'm def affected. 2 drinks and I'm drunk. But about an hour later I'm totally back to normal again.
I'm almost 2 years post op now and I drink fairly regularly (particularly since COVID started!), though I still stick to red wines and spirits with no sugary mixers for the most part (with the exception of Kahlua, an important ingredient in espresso martinis)
P.S. I am NOT advocating drinking to all, especially if your team advises against it. Everyone is different and should aim to know their limitations and stay within them. Some may have more trouble with this, which is probably why lots say to just stay away. It can become a slippery slope....
Edited to add: I just realized the title of this thread was for bypass. Oopsies, I'm a sleeve, and I think it may be a bit different, between the two: alcohol will bypass a portion (or all?) of the small intestine in by-passers and go directly to the the large intestine, which results in different alcohol metabolization rates...