Avoid foods that are too likely to cause tooth decay, such as meat, candies, and sticky sweets. Instances have been reported of food allergies having caused bad breath. Search out the foods you are allergic to, and avoid them. In cases of bad breath caused by stomach problems, thyme tea can be helpful. Boil your toothbrush each month or buy a new one.
Bacteria grow on the toothbrush.
Rinse it with hydrogen peroxide occasionally during the month. Chew fennel or anise seeds after eating an odorous meal. Do not use commercial mouthwashes. They irritate the mouth more than they solve any problems. All they have is alcohol, dye, and flavoring.