The theater I go to already serves Burger King, Pizza Hut and Taco Bell. Can’t see that the other stuff you mention would be any worse. I just doubt that much of anyone going to the movies really wants a tub of raw veggies to snack on while they watch the show.
Ewwww, do you have fabric seats? Sitting on spilled Coke is miserable; sitting on cheese, oils from taco's or pizza would be unpleasant in the extreme. How could you ever hope to get the grease out of the fabric?