Plastic containers often absorb odors from the objects left inside them. This is especially true for the pungent aroma of onion. A plastic container used to store a food product containing onions may have a lingering scent even after washing it with soap and water. You can remove onion odors from plastic containers by utilizing some inexpensive household products.
Sprinkle the bottom of the container with baking soda.
Fill the container half full of white vinegar.
Fill the container the rest of the way with hot water and let it soak for several hours.
Soak the container's lid in a solution of equal parts hot water and white vinegar and 1 tbsp. of baking soda. Do this for several hours as well.
Wash the container and lid in hot, soapy water.
Rinse the container and lid in clean water and dry thoroughly before storing.