Bad breath can stem from a variety of reasons. From bad bacteria on the tongue to some medical conditions such as dry mouth (also known as xerostomia), oral infections and other oral conditions, and even acid reflux. By fixing the root cause, you can tackle halitosis.
In general for bad breath here are a few tips and foods:
Stay well hydrated
Vitamin C rich foods can help neutralize odors
a plain no sugar added Greek yogurt
avoid super low carbs diets
avoid dehydrating drinks like coffee and alcohol
fresh parsley and basil