I've seen a few people attempt to open a "cereal milk" restaurant, where you can order CocoPuff milk, Cinnamon Toast Crunch milk, Fruity Pebbles milk, etc.

The few I've seen have flamed out pretty fast, which is predictable for an idea that was obviously cooked up by a couple of rich college kids while passing the bong, and then convincing their wealthy fathers into coughing up the starting costs.