why bring it?  Alcohol is not necessary to bring to a date.  In fact, as an older guy, I find it to be an erection inhibitor, so I usually lay off the sauce for at least a day or two before a date.  I suggest you just try to relax and enjoy, experienced providers are used to nervous guys.  Hell, I'm still nervous when meeting a provider that I have not seen before.

Swim

most ladies prefer it's in an unopened bottle. That's why a bottle of wine is so popular.  If you bring a flask of scotch and offer to pour the lady a drink, she may refuse simply because you're pouring it from a flask. I know it may sound strange but remember the lady doesn't know you from Adam, and their are weird guys out there that might put something in the scotch.  Another popular gift are  candles, relatively inexpensive and most, but not all providers like candles. Don't forge to bring matches, many providers don't smoke.  The simple rule of them, whatever you bring, adult toys, booze, condoms,etc. most if not all ladies want it in the original packaging so that they know it's new and hasn't been tampered with .  Good luck  

but stay away from the booze.  She'll be used to nervious clients...  but probably very intolerant of drunks.   Be well washed, have the right donation, be respectful, you'll do fine.  Water is good...  anything you bring to share or for her should be sealed, opened by her or in front of her.  Gals today...  providers are no exception...  need to be cautious about having their drinks tampered with.  
If you have a dinner date, you may order what you want...  but just 1...
H

It might send the wrong message.

If later you learn that she has a jones for say, Patrone or some specific then have at it.

And leave the liquor out of the equation.  This isn't a first date, it's an appointment to have sex. If you take out a bottle of booze and start doing shots to calm down you are going to leave a questionable impression.  Some gals will out-and-out toss you out of the room if they think you are drunk.

..... I would never imply you/he BYOB.  Now, if you are into Louis XIII, I may have an issue - lol.  In all seriousness, I prefer wine, and if a gentleman reads my site, and brings a bottle, it is always appreciated.  Ladies, keeping a well stocked liquor cabinet, goes a long way.  I also have gentlemen that do BYOB, and it is never shared; just stored, until their next visit.

Hugs and Kisses