A friend had to give her mare electrolytes last night since she wasn't drinking much water. Since she loves gatorade, she mixed a bottle of gatorade with electrolytes and she drank that enjoyably and then went back to drinking her water!
When I showed 4-H and FFA market steers I gave them a bottle of GatorAde mixed in their water bucket to encourage drinking. Nothing like showing ganted-up beef cattle...haha.
Short term or a once in awhile shouldn't be an issue, I wouldn't think.
In the hot and humid summers of east TX or a really hard workout I would give an electrolyte supplement to my horses. I used the same stuff I seen the race horse people buy(Electro-Dex?).