I had a draft mare who, in her former life as a work horse and with a different owner, was only watered in the morning and then in the evening when returning to the barn. She was, unfortunately, conditioned to never drink while in harness and thus under saddle. I tried everything; flavoring water, bringing our own water and I could not get her to drink anything, anytime, anywhere. I was a very stressed out horse mommy in the beginning!It took a few months of travelling many miles to many venues but she finally realized she had to drink SOMETHING.Horses have terrific instincts and they really will drink when they need to if we moms stop fussing over them.My mare figured it out at our overnight shows and she did actually drink when she was in a stall and I wasn’t there peering through the bars. The more difficult situation was always when she was tied to the trailer at a one day event. It’s just very important to help them stay cool in every other way possible until they choose to hydrate themselves. Try flavoring at home and then carry your own water (flavored) with you. I always save gallon milk jugs with screw on lids, wash them in the dishwasher and take a half dozen of them in my trailer or back of my truck in a big coo!er. Good luck and don’t stress!