Cold and Flu Season: How to Naturally Clean Your Toothbrush We should really wash them out at least every two weeks. Even more frequently when an illness strikes the house. How? 1) Soak them in a cup of vinegar overnight. (or peroxide) OR 2) Soak them overnight in a solution of water with a few drops of anti-bacterial essential oils, like thieves, rosemary, clove, or cinnamon oils.