This is something I have tried after trying an enema and aquarium pump. I've tried continually drinking water through a straw. So far, the most I can do is 1.5L but 2L will probably be where I will stop.
Initially, I was trying to find a way to increase my capacity and found professional eaters sometimes use water and food. I didn't want to do food but drinking a gallon at once is somewhat impressive from what I read. I'm not interested in stuffing and I don't plan to become a professional eater, I just want to create more available space.
Has anyone else tried this or has thoughts about it?
I'm sure there's a Wikipedia article on stomach capacity for definite numbers and such, but I do know there is a definite limit to how much you can hold. Once you reach this limit, any more food or water is simply rejected. You will throw up. How competitive eaters manage it, I have no idea. Suffice it to say, however much it takes to make you feel sick to your stomach, that's likely how much you'll ever be able to take.
Sorry to sound like a downer. A rerun of Mythbusters just recently aired covreing a very similar subject. They basically concluded the average human stomach has a capacity of slightly less than 1 gallon. It varies from person to person, but that's usually it. Any more and you simply can't hold it, so the body get's rid of it. That's why people usually throw up after a "milk challenge" and how the Lap Band surgery works.
Just a little more. You can take it...I hope...