There are quite a few "arousing" or "sensitizing" gels/creams for the ladies. I've used a few on partners over the years. Some seem to be little more than flavored lube (maybe just to get some fellas more willing to perform) others have had menthol or peppermint or something similar to enhance sensitivity. Some taste fine others not so much.

I'd be disinclined to go down on a lady with a mouth full of hot water (containment it's self would be an issue) but a drink of hot tea or coffee to give you a hot tongue does create a different sensation. Similar with cold, don't apply an ice cube directly to her but have it chill your tongue then go to work.