There are several ways to kill bacteria in the mouth, including natural remedies and good oral hygiene practices. Here are some tips from the search results:

1. Brush your teeth twice a day: Brushing your teeth is the best way to remove unwanted bacteria in the mouth. It helps to remove food particles and plaque, which is a sheet of bacteria, from your teeth.

2. Floss daily: Flossing helps to remove bacteria and food particles from between your teeth and along the gum line.

3. Use mouthwash: Mouthwash can help to eliminate remaining harmful bacteria in the mouth. Certain mouthwashes contain active ingredients that kill bacteria and reduce both plaque and gingivitis.

4. Use natural remedies: Some herbs like neem, clove, and green tea have natural antibacterial properties that can help kill bacteria in the mouth naturally. Oils such as eucalyptol, menthol, and tea tree can also help kill harmful bacteria in the mouth.

5. Avoid sugary foods and drinks: Bacteria in the mouth thrive on sugar, which helps them multiply rapidly. Avoiding sugary foods and drinks can help to reduce the amount of harmful bacteria in the mouth.

6. Stay hydrated: Drinking plenty of water can help to flush out bacteria and food particles from the mouth.

7. Visit the dentist regularly: Regular dental check-ups and cleanings can help to remove plaque and tartar buildup, which can harbor harmful bacteria.

In summary, good oral hygiene practices such as brushing, flossing, and using mouthwash, along with natural remedies and a healthy diet, can help to kill harmful bacteria in the mouth and promote good oral health.