Truth and Consequences - S3-E7
Plot hole: In this episode, it is discovered through a scientific study that Eric does not dream, and in fact doesn't even register brain activity while he is sleeping. However, the season 2 episode "Wrong Side of the Tracks" features a subplot where Eric listens to a motivational tape while he sleeps so he can learn to ice skate, and he dreams of Nancy Kerrigan giving him a lesson.
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.