It’s simple.... u r not compatible. Trust me!

I suffer from bad breath as well. There is a mouthwash that seems to help alot called smart mouth they sell at walmart. It keeps my breath fresh for 10 or 12 hours after use. He should also see a dentist mine is caused by periodontal disease and often people let it progress for too long before diagnosis and end up losing teeth.

Honesty is the best policy.
Tell.him
" I've told you before your breath f****** stinks ! ".

Watch some popeye cartoons

Sorry, but I don't follow the frequent and ongoing Popeye references.

Get one your girlfriends to tell him in secret

This seems like a useful idea. There must be one of your friends with a modicum of tact and diplomacy , and who he likes and trusts well enough to have a confidential conversation.