Hi ! gone through your query.
Diabetes is one among the medical conditions causing
halitosis.
You did not post blood sugar levels. check HBA1C every 3 months.
Make sure diabetes is under good control.
Get professional scaling done every 4-6 months.
Brush twice daily. Floss once a day.
Mouth wash thrice a week(diluted in 1:1 ratio with water).Do not overuse mouth wash.
Smoking,other tobacco habits,old unclean denture and
gum infection can also cause this.
Diabetics,liver and kidney disease ,
tonsillitis and other respiratory infections potentially cause halitosis.
Check if you have a low salivary flow.
If any of the above includes your general health, this has to be corrected immediately.
Use saliva substitutes if you suffer low saliva flow.
Keep away garlic,onion,tobacco products.
Have plenty fluids., 3-3.5 liters per day.Keep hydrated.
regards.