We have six kids. If each child got a drink at each meal and a drink mid morning and mid afternoon that would be a minimum of 6 x 5 = 30 cups per day to wash. That just doesn't work for me so. . .
We have assigned cup colors so that we never fight over colors :) After meals the kids put their cup in "cup-land" next to the fridge. If they have milk with a meal we rinse it out before they put it back. After dinner they put their cups in the dishwasher. It is a simple thing, but it makes our lives a little bit easier!