Hi.. Thanks for the query.. As per your complain bad breath also known as Halitosis can occur due to a number of causes like poor oral hygiene, oral and dental infections,post nasal drip, sinusitis, acid reflux,respiratory infections, diabetes etc.. However gastritis or stomach upset is a common reason for bad breath but if it is not relieving with the treatment then you should consult an Oral Physician and a thorough clinical evaluation and investigations depending upon suspected cause can help in diagnosis.. Treatment of underlying cause will relieve the symptoms.. As of now you should start gargling with a flavoured mouthwash twice a day.. You should chew flavored sugarfree chewing gum.. Do warm saline gargles twice a day.. Limit the intake of high aroma foods like onion and garlic.. Drink plenty of water and maintain a good oral hygiene.. Hope this helps.. Regards.