I call this prank a leaky sink for no reason at all. Anyway, heres what to do.
1.Get some scotch tape (Look at the photos)
2.Be sure you're victim's sink has one of those hose things
3.Take some tape off the roll and tie it around the spout's handel. Be sure the tape is tight on there!
4.The finished thing should look like this. *Look at last picture*
5.Watch as the victim ignores the hose and turns on the sink, thus spraying them.