I have actually seen this one first hand while in college.  The goal is to drink a gallon of milk in an hour without vomiting.  Very popular in college as a form of hazing.  Apparently, the stomach can actually only take about a half gallon of milk at a time before the gag reflex kicks in.  Not exactly a smart activity to take part in.  This challenge was listed in Kitchen Daily’s Top 10 Most Dangerous Food Challenges.