My horse absolutely will not drink at competitions. Now I take some speedi beet and make up a real sloppy bucketfull which he will slurp away at. Definitely worth a try
I add a little apple juice to the water, that seems to do the trick. I also use soaked hay for travelling and at shows which helps with hydration as well.
I agree with the SB water but another good tip is chop some apples & carrots in the water. Most horses can not resist fishing them out, therefore getting some water at the same time. We always do this on long journeys abroad.
My sister's pony won't drink at events and doesn't like sugarbeet so we syringe water into his mouth. Most of it washes striaght back out of his mouth but it has to be better than nothing.
Can't really help my old SJ was wierd and drank more at shows. Wouldn't drink out of a bucket in his stable though. I tries putting apple pieces in his bucket at home and he just looked cross and wet!
Taking water from home is often the best option for a one day show. It also saves on the long, damp walks to and from the hosepipe.
Putting something in the water is the traditional approach but you have to do it at home as well to get the horse used to it. Apparently peppermint is particularly good as it covers different smells more effectively than apple juice but I would think it would need some experimentation at home to make sure it wasn't putting the horse off.
I used to have some fantastic electrolyte powder the horses loved, made by Plusvital, which encouraged them to drink but it's been discontinued. Some of the current powders seem to put horses off but if you find one your horse likes it can be another option for a day here and there.
My horse over does it at shows and loves to drink - makes a rael fuss about it. My sister's however is not the same and will swill his lips in it and that's about it. It doesn't worry me too much, I knwo they have plenty of water at home so will be hydrated enough and I'm sure if they were really thirsty they would sip it.
Mind you, my sister's horse did decide he'd much prefer to have some coca cola on monday as opposed to water maybe he needed the caffeine hit!!!