sick or severely dehydrated animals may need help maintainingng osmolarity ( ratio dissolved stuff to fluid) in their bodily fluids, so you give them an isotonic(same ratio as should be found in bodily fluids) solution so that they can easily re-balance themselves in a way.

Amphibian people use frog ringers solution on sick frogs etc. same idea

I would imagine gatorade has too much sugar and wouldn't be good. But if the animal is not dehydrated there should be no need for any of this

*I hope this made sense, i'm kinda shot...