And Then There Was Shawn - S5-E17
Trivia: Eric makes two references to South Park in this episode. When he first greets everyone in detention, he says "Hidee ho" in the same manner as Mr. Hankey the Christmas Poo. Later after everyone discovers Kenny has been killed, he screams "Oh my gosh, they killed Kenny!"
Chosen answer: In the present day, with the United States abiding by more stricter school health laws, for the most part this wouldn't be in school cafeterias as many cannot even have carbonated beverage machines now. However, in the 90s when the show takes place, it wasn't unheard of for there to be coffee machines in the cafeteria of small schools where the teachers eat with the students as we see them do often in the show. The idea being that the cafeteria was small enough so a teacher or hall monitor could catch a student before they could drink the coffee.