If your snake is seriously dehydrated, the vet will give it booster electrolytes -- mine did when I got a sick snake in December. As long as you're taking care of your snake and this isn't a rescue case (as yours looked fine), there should be no need for any added substances in its soaking water, but if I added anything it would be up to a tablespoon of Pedialyte because I suspect it has less unnecessary gunk than Gatorade.