The solution is simple. Speak up. "Dude, you have breath that will peel fucking paint. I have a disposable toothbrush. In the bathroom. Go. I'll be here when you get back and we'll have a lot more fun. Promise". The guy would probably rather have a decent session than get his panties in a twist over his breath. Unless he's a thin skinned douche, and then so what? Unless it's like a digestive disorder that's pulling gut gas out the sewer vent, then you just gotta say you can't do it, sorry, let's fuck. Doggy, please.
It's OK to tell the truth in these encounters, and everybody who plays this game needs to leave their ego baggage on the doorstep. Both parties need to do whatever is required to make the session a hit. If a hygiene issue pops up, deal with it head on (no pun intended).
I'd go see Lindsey, especially now that I know she has a gag reflex

j/k