the reason you puke is because your stomach is not 1 gallon large, so you cant hold it in also milk is processed slowly in your stomach which is why if you drink a glass of milk on an empty stomach you will fool yourself into thinking you just ate something. Its very funny to watch people think they can though.
Jackass trying to do it as fast as they can 😂
http://video.google.ca/videoplay?docid=2091838742330346535&q=1+gallon+milk