Always start bathing your horse by spraying the water on their back or front legs first, that way they know waht is coming and how cold the water is, etc.
With my horses, here is what I do.
I spray both their legs first, usually the back an work my way up with the water. Then I spray their hind end and slowly work my way towards their shoulders, making sure that they are okay with it.
If there is a bathing stall I usually tie them up, but when there isn't then i hold them. Sometimes they will dance around in circles when I bath them just because they don't like to get wet. I keep moving with them, spraying the water on their legs or body until they stop moving, then I stop spraying the water on them as a reward for holding still and not worrying about it.
If they are tied up and move around, I just let them. They can't go anywhere far so they can deal with it, hehe!!
When I get to their necks, I stand next to their head and spray their neck towards their hind, so now water unexpectedly splashed up in their face or ears.
When I wash their face I always do it with a sponge, its better so the water doesnlt get in their ears or in their eyes, etc.
Chocky, our youngest horse, wants to drink the water. He will literally put his mouth in front of the hose - no matter what setting it is on if there is a head on it, when there is he prefers the shower option or center. - but he will drink the water like that. it is so cute!
Then Golley, he just hates water. he will dance around for a bit - but after a few minutes he realizes that he won't be getting away with it and gives up.
It just takes time and lots of patience if they don't like it.
🔫 Don't Tread On Me 🐍