Have a camper standing behind a table as a prop for a sink, with a cup and a bottle.
Camper 1: Time for mouthwash! (Pretends to pours mouthwash from bottle into cup. Pours “mouthwash” into mouth.)
Camper 2 (walks on stage): Where's the last of the mouthwash? (Notices that Scout 1 is using it.)
Camper 2: Can I use that after you?
Camper 1: Pretends to spit the mouthwash through camper 2's ear. Camper 1 makes their mouth look like it has no mouthwash in it anymore and Camper 2 makes it look like they have water in their mouth.
This continues as several more actors come on stage until you get to the last person. This person will They will have already put real water in their mouth and will spit it into their cup and exclaim loudly “[Camper 1's name] what did you have for dinner???!!!