Spoon or ladle
Not to go overboard with camper personalities, to stress the humor that the campers were drinking dirty
The counselor walks on the stage with a big pot, sets it down on a table along with a spoon or ladle, and sets up a “Back in 5 min” sign before walking offstage.
A camper comes along, eyes the pot, grabs the spoon and takes a big, messy slurp. Eyes wide, he/she grabs a friend from offstage and stresses how important it is that they try this awesome tasting soup.
This keeps happening, each new person getting another to try the soup. You can make each have a different personality just for laughs.
The counselor walks back on, seeing the camper grouped around the soup. Spotting the counselor, the campers flee.
The counselor reaches into the pot and brings out a pair of dirty socks and remarks how clean they are after soaking.