Can drinking too much water at one time as gulping expand or stretch stomach pouch?

No. Tho you overfill your little sleeve its not gonna feel great. Possibly throw up.

nope. Your stomach will let you know if you're overdoing it.

It's actually really hard to stretch your stomach, and in fact that may be a myth, according to some recent research (though I can't say for sure).

Water and other liquids just pass right through the pouch. You NEED to be hydrated after surgery for many reasons, so do drink as frequently as you can. As others have said, you can't really "gulp" especially right after surgery. Now at 5 months out I can gulp a few times, but I can't chug a lot like I could before surgery.