Why yes I use 3 ounce plastic bathroom cups as pots! At about .02 cents each they are very economical, easy to write on and believe it or not I reuse them. You will need the assistance of a soldering iron to burn a couple of holes in the bottom.
When it comes time to reuse some of the old "pots" I fill one of my kitchen sinks with hot water and 2 cups of Clorox bleach. I toss in my dirty pots and let set for an hour. I dawn my handy-dandy latex kitchen gloves and rinse them out. Not only does all the all dirt come clean, if you take your thumb and rub on the name that has written on the side with a Sharpie, it comes right off!
Where to buy? Originally I purchased the Solo brand 3 ounce bathroom cups at my local Wal-mart but they are impossible to find in my area. Luckily, Kroger stores which also owns and operates Ralphs, King Soopers, Food4Less, Frys and Smiths started carrying their own version of these 3 ounce bathroom cups. Their cups are actually about 1m stronger than the Solo brand bathroom cups.
Don't have one of these stores handy? Try www.buythecase.net. They have the 3 ounce Solo brand bathroom cups that you can mail order.
Safety warning: When burning holes in the bottom of the bathroom cups be sure you're in a well ventilated area (preferably outside on a day with a slight breeze) and wear appropriate protective clothing and devices (e.g. facial mask). Soldering irons are also very hot so keep out of the reach of children when in use.