What could be a cure for some medical conditions that causes bad breath?

Which one? Is this a hypothetical question or related to your own bad breath issue? If it's a hypothetical one, space is limited here and you can research it by doing a google search. If you yourself have bad breath, first rule out any dental causes by seeing a dentist. If your dentist feels the cause may be medical in origin, he\she will refer you to a physician to check you out medically.
Depends.. .. On which medical condition is causing the bad breath. Gum surgery can treat periodontitis. Antibiotics can treat sinus infections. All the best..