The best mouthwash for tonsil stones is one that contains ingredients that kill bacteria in the mouth. This mouthwash kills bacteria that can cause tonsil stone formation and helps to prevent them from happening. Mouthwash can also be used to maintain healthy pH levels, reduce debris and prevent gum disease. However, it is important to use the right amount, as mouthwash that is too strong may irritate the throat and make the condition worse.