Do you only rinse it with water and accept stains? Boil it? Soak it in bleach? Put it in the washing machine? Put it in the dishwasher? Are they disposable? 
To sterilise and degrease it, you can put it in a bowl of hot water with baking soda, and then steam it in a pan for half an hour, or better still, use a pressure cooker. Microwaving it works too but can be a bit messy - I do that to my dish sponges and small kitchen towels 