To get this achievement you'll have to select the Camel (Humphrey Ciabatta) on the Payday map. Then take this character to the casino. There will be several NPCs dancing on stage. You'll need to spray each one of them with the Camel. On an Xbox controller Y (Special Use button) will spray and X (lick button) will draw in more water. If you don't get it at first, just continue to spray everyone in the room with water until it pops.