Bad Breath?

This is Larry Joe. Larry Joe is my first ever basset hound and I got him as a rescue about 2 years ago now. He has always had a bit of plaque build up on his teeth. For the past year or so his breath has been bad and by bad i mean baaaddddd. Like makes me wanna vomit bad. I brush his teeth and it’s good for a day and then right back to smelling like satans butthole. I’ve only ever owned bully breeds and never experienced breath like this before. Any recommendations on how to help him not be such a stinky man?