Water has not proven to be enough for me and I drink about 6-7 17oz bottles a day
I just got this delivered today and it seems to be helping:
Amazon.com: Rain Spry Dry Mouth Spray By Xlear with All Natural Moisturizing Xylitol to Help Prevent Cavities and Keep Mouth Moist) 4.5 Oz: Health & Personal Care
IIRC xylotol is a sweetener used in a lot of sugar free gum. I wonder how well it takes heat? If it vapes one could try putting it in the liquid to counteract the drying effect instead of sucralose or another sweetener. That's going to want some study though. You don't want it turning nasty somehow when it mixes with other stuff.