Hi.. it couldbe due to the deposits or calculus present on teeth in your mouth.. bad breath could be due to multiple reasons..whether it be mouth breathing at night, due to certain foods like garlic, onion, starch food etc. Kindly visit the dentist for a proper diagnosis and if deposits present then get scaling or full mouth cleaning done . Hope this helps..
Next Steps
Maintain with mouthwash and brushing at night.
Health Tips
kindly do not ignore.. as its could be periodontitis or pyorrhoea or infection of gums.