2-Distilled Vinegar
Pour some distilled vinegar into your stained Tupperware, ensuring the stain is fully covered. Let it soak in for around 30 minutes. Gently scrub the stained area and rinse. Clean as usual, and you'll notice a difference!
3. The Sun

Real Simple
What better natural cleaner is there than the sun?! Rub some lemon juice over the stained container. Then, let the container sit in the sun for a couple of hours. Wash and dry the container as you normally would.