1.Mint mouthwash masks it. That's why it always comes back.
You rinse, and for about an hour you're fine. Then it's back — so it's gum, a mint, another rinse, all day long. That's the treadmill: mint only sits on top of the smell. The film that makes it never moved — it's still stuck to your tongue and gums, so the smell just crawls back up through it.
See What Yours Pulls Out