hmmm?
I'm still pre-op so I can't speak from experience, but I did read that since you pretty much just have a hole in the bottom of your stomach instead of a valve, as long as you drink slowly, the liquids will keep passing right through your pouch. For this reason, you'll be able to drink more than what you would be able to eat.
Again, can't speak first hand; it's just something I came across while researching.