I must repeat this each time the guide is mentioned: it recommends to drink salt water to prevent dehydration. I don’t know yet if it’s just idiot or sheer criminal.
“Salted water helps you retain body fluids. Although you get more thirsty, if you drink salted water the risk of dehydration is lessened.”
You do need some salt as you re-hydrate after sweating a lot, to keep your electrolytes in balance, though it is easy to over do.