When there is a task, such as drinking from a water fountain, where the number of repeated actions (gulps, in this case) is arbitrary, I always choose a particular number for a particular reason. Every number from 1 - 15 has a specific association for me, so I will choose it based on what kind of juju I think is required. For example, the number 5 represents humanity to me, 6 the devil, 7 God, etc.
Also, whoever said 4 is the perfect number, 4 is one of my lucky numbers (was my soccer number as a youth).