They can survive being in a cup. They don't need oxygenated (?) water, they breathe air. Although I do think they do better in a larger environment. My manager at Petsmart was telling customers they can be kept in the cup you by them in..I didn't like that too much. It's not much money to buy a simple bowl or vase at walmart in the crafts section. And usually if they don't want to buy a bigger bowl, they won't want to clean the cup, and it will get dirty and the fish will die. And the rice paddies aren't 4 inch deep holes in the ground. These are rice paddies:
http://www.douglassteakley.com/images/ms1016b.jpg
But the cups are the easiest ways to house them short term. The reptile/fish specialty a couple of towns over actually has these glass bowls with squiggly edges, they're at least 2 liters, they fit right on top of each other and still let air in-it's very nice to see a little bit of change. Of course they charge more, but at least its not just a cup.