Yes, I didn't make clear that electrolytes don't need to be in the water. It is easier when they are, though, because just relying on food, if you don't have the right food, or if the heat and exercise makes you nauseated, can make it difficult to get the right balance.

Potassium is important to supplement, but not quite as easy as sodium to get from salty snacks like crackers or nuts. Potato chips are actually an excellent source of both. When I exercise I crave potato chips. If I'm not exercising I don't eat them. Potatoes are high in natural potassium, and the salt replenishes the bodies sodium needs. Lightly salted potato chips are best.

Most people get nauseated hiking in the heat, though, which is why sports drinks can be beneficial. Just limit the sugar content. I believe I have posted recipes for homemade sports drinks in the past - an archive search would find those posts. After doing that research I bought a potassium chloride salt substitute that I keep in my kitchen. When I start feeling the effects of low potassium (which seems to be a problem for me) I'll add that to my food or drinks for the day. I also sometimes take a potassium supplement, but you have to be very very careful with potassium because too much can cause cardiac problems.

Along with sodium and potassium, calcium and magnesium are important electrolytes that need to be supplemented if you're not getting adequate amounts in your food. The body does obtain these instrinsically (from bone) when needed, but having them available from food or drink helps speed up their distribution to the body.

Alternating sports drinks with water is one option for maintaining electrolyte balance while exercising. Carrying food high in natural sodium, potassium, calcium and magnesium are a good way to fuel your body's needs while you're resting (i.e. in camp, not exercising, and hopefully no longer nauseated).

MNS