1 Clean the plastic containers in hot, soapy water, using a nylon scrubber. Rinse well. Never use metal scrubbers on the containers, as they can damage the plastic.
2 Remove the stains by trying one of several methods. Try covering the stain with a liquid automatic dish washing detergent (one plastic company recommends Palmolive) and allow it to stand for about 30 minutes. Rinse thoroughly.
3 Soak the container in a solution of 1 tablespoon of liquid chlorine bleach to 1 cup of warm water. Allow it to sit for thirty minutes. Rinse until you can no longer smell the bleach in the plastic box.
4 Remove exterior stains. Try using Bar Keepers Friend (or Cameo or Dawn Power Dissolver) and a nylon scrubber to remove stains. Rinse thoroughly.
5 Try an oven cleaner for exterior stains. Make sure there is adequate ventilation. Wear gloves and pour the oven cleaner on the stain. Allow it to sit for the time recommended on the can. While still wearing gloves, use a cleaning cloth or sponge to remove the oven cleaner. Do not reuse this cleaning cloth until it has been laundered. Do not reuse the sponge at all. Discard it. Rinse the plastic container thoroughly under hot running water and wash with liquid dish washing detergent with a fresh sponge or cloth.