Consult with a dentist or a medical doctor. Bad breath can be the result of many causes, even disorders not related to the mouth directly. Conditions like diabetes may cause mouth dryness which will result in bad breath. Diabetic ketoacidosis may also cause a fruity smell to the breath which may be perceived as halitosis. Speak to your dentist about the possibilities.

Yes, your approach is correct but your husband needs to be willing to address the issue. I would first advise that he visits a dentist and only once a dental problem can be excluded, he should visit a physician for further investigation. By ‘cleaning the stomach’, I assume you mean purgatives to induce diarrhea and vomiting, a common practice in your country South Africa (I noticed your email address) and this could contribute to halitosis but it is unlikely. His chronic sinusitis could be contributing to his halitosis and once again, he needs the assistance of a medical specialist.