I was interested in hydration, so I looked at what doctors use (google "oral rehydration salts"). I've tried to make a cheap substitute for the store bought stuff by adding some sugar, Morton salt lite (which contains both potassium chloride and sodium chloride), ordinary table salt and baking soda to my water bottle. My recipe, which I'm not sure is optimum, is:
2 Tbs sugar
1/2 tsp Morton salt lite
1/2 tsp table salt
1/4 tsp baking soda
mixed into a little over 1 qt of water (I try to err on the side of too much water).
Keep in mind that I'm not a doctor. I'm just a guy who was interested in the subject and did some internet research. This recipe may not be any good.