I almost completed this bet last night.
A group of friends and I were at a party. We decided to have a contest of sorts -- whoever could consume a gallon of milk in an hour would be the winner.
That's right, I was stupid enough to take it, even after reading this node. I was even stupid enough to keep going after everyone else involved quit. I had already won by default and yet I kept on chugging.
But, I had thought it out. I followed howlingfrog42's strategy of chugging the first half gallon (which I accomplished in the first 10 minutes), waiting, and then downing the remainder. I had requested skim milk, which helped a lot. I was also popping generic lactaids like crazy. N.B.: I'm not lactose intolerant, but I figured for a whole frigging gallon, I'd need some more lactase in my stomach. Now, a single dose of the stuff is 3 pills. I took six with my first gulp, and I had taken about twelve by the time I had consumed the half gallon.
After finishing the half-gallon, I began to have second thoughts. But I waited, and urinated once or twice, and my stomach felt fine -- and so I continued. With 10 minutes left on the clock, I popped a few more magical lactase pills and started drinking again. At this point, my stomach began complaining. I weighed the possible outcomes: the joy of winning a stupid bet versus the high probability of vomiting, and eventually decided to stop.
I had consumed 7/8ths of the milk. And besides some minor stomach pains for about half an hour afterwards, I felt fine. Didn't even throw up.
Next time, I won't eat anything for the whole day, just to prove that drinking a gallon of milk in an hour can be done.