...in the shower so telling her she has bad breath is no biggie.

Also, you shouldn't floss within two hours of seeing a provider.  See link...

Saw a gorgeous and very, very highly reviewed provider the other day.  Perhaps she hadn't brushed her teeth or used any mouthwash after her morning coffee but she had really bad breath.  It was a total turnoff and I had no idea what to do.   It kind of ruined things for me.  I mean I went through with everything but kissing and even just talking at close range was killing me.   Is there a polite or considerate way to ask a provider to use some mouth wash if she has stinky breath?  And for future reference is there a way I could get a provider to freshen up her breath once I arrive so this doesn't happen again with somebody else?

I have to admit, after sitting here and staring at the screen, I can't think of a good way to do it.  You could, as a matter of habit, carry a pack of mints, take one for yourself in front of her and offer her one.  Hopefully, she will get the hint and follow your example.

...since I have them on me.
I usually pop one in my mouth as I make my way to the room.
Smokers breath and coffee breath, not my favorite things to encounter.

before an appointment she should NOT be an escort. Period.

should not have to tell her this.  

But it's all in the way you say it, which is the tough part. Just be nice about it. If she gets mad, that's strike 2 lol.

If she's well reviewed, this probably isn't a common problem with her. Maybe she forgot part of her routine or that she ate something after she brushed her teeth. Try to be polite about it, but there is no way to avoid embarrassing her. But this could well be hurting her bottom line if it happens with other clients. So, if she's not a fool, she'll appreciate that you brought this to her attention.

"I don't know how to tell you this but your breath...  I thought you'd want to know."   It is easier said than done.  I'd speak softly & kindly.  It can happen to anyone.  Possibly even after doing "everything right".

I think you should tell her.  It's her business and if she's going to be professional...she needs to take care of herself.  If you meet up with a new girl...mention your bad experience with this one and just stress that you'd appreciate it if she brushed right before.  She won't take it personally, because you're not talking about her specifically.

and if you want to spare her feelings and not risk spoiling the mood, you can always say that "maybe both of us could use some?"

Regardless of HOW you do it, it needs to be done. Anything is better than suffering through a session of funk breath, do you (the OP of course) really believe that the lady would have any qualms about telling you if the situation were reversed?

The approach has to be kind though. Kissing is something that if done with bad hygiene can leave you with a bad taste long after. I wish everyone realized this. Last thing I want is a lasting stench for the rest of the day, regardless whether it's in your nose or in your mouth. Scents are awesome if they're pleasant, unfortunately the bad ones linger as a reminder. Nothing better than the scent of a man, it's a huge turn on. I believe it's the same case for gentlemen when engaging with a woman. Let us know, the hint of "freshening up" should work (mutual shower and when you gargle hand her the rinse). If they're still clueless honestly I don't see them again, to me it feels they get off in the fact they smell or are dirty and want you to suffer through. I'm not one to suck it up twice. If you stink or are dirty and request me to perform a service I "may" suck it up once but you won't ever see me again. There's no excuse to be disgusting even more to be clueless about it!

And it goes both ways. You either piss them off royally and the session sucks or they are professional and run off and deal with it.  

you could TRY to say( maybe before you start the action not when you walk in) " I'm gonna rinse with mouthwash first. do you want some?"

I am very self conscious and concerned about my breath, maybe more than I need to be.  So just to put *myself* at ease, I actually tell all new guests to let me know if anything can be nicer during their stay - "temperature, music, if I need a breath mint. Anything."

We could eliminate the pit check and breath check, which rarely works. I always bathe right before a session,  if I need to I'll ask to freshen up when I arrive. It's important to me to be squeaky clean, I'm all up in your face in more ways then one.

I like that. Putting two in your mouth and sharing.