Do not try this at all

So, there's a somewhat well-known urban legend — or at least, one that I've heard mentioned by a few different people — that it is impossible for a human being to consume a gallon of milk in an hour. This legend is usually phrased in the form of a bet, such as, "I'll give you (pittance) dollars if you can drink a gallon of milk in an hour, without throwing up." Especially cruel/miserly people will often attach other stipulations to the bet, such as not being allowed to consume any other foods or liquids during the challenge period, or not being allowed to throw up for another hour or two after the initial time window has expired. The idea is apparently popular enough to have been christened the, "gallon challenge."