I don’t allow my horse to drink from a water trough other horses use, you never know the health of all the horses that have used trough.
I carry his own red buckets, don’t know if he can see color or not. I put his water and hay where he can eat and leave him alone to relax.
I get those big blue water containers from Walmart and fill with water take 1 or 2 depending on how much needed, if I am not sure of water where I am going.
In a pinch usually some type of store/gas station where water can be bought is around, unless out in wilderness.
But my horse is not real picky, drinks beer from a red solo cup. lol