What is a good way to cure post nasal drip and stop bad breath caused by it?

See Dentist then ENT. First try to determine the cause of the sinus problems. An infected upper tooth can cause chronic sinus problems. If there are not dental problems then see a physician or ent.
Solve the drip. The best long term solution is to find and treat the cause of post nasal drip.

Related Questions

Any medicine to cure post nasal drip which causes bad breath.

Decongestants. Decongestants can be taken orally in pill form, or nasally, in spray form. These treat symptoms only.Get examined and find out what's causing your problem. You may have inhalation allergies, it which case your dr.. May wish to treat differently. Read more...
See ENT. I suggest that you see your primary care physician or an ENT specialist to discuss your situation. Also see your dentist to rule out other causes of bad breath. Read more...