If your bento box has retained an odor from something that has been stored inside, we recommend using this method to remove the smell:
1) Mix equal parts baking soda and water to create a paste. 2) Rub the paste onto the container and let it dry. 3) Dip a soft cloth in warm water and wipe away the paste. For strong smells, dip a soft cloth in white vinegar and wipe away the paste. Dip a soft cloth in warm water and wipe away the vinegar. 4) Dry the metal with a cloth to prevent water spotting.