Drink the most distilled water you can find.
The author also should have stressed that the benefits of kombucha, yogurt, etc. come largely from fermentation.
Electrolytes are really just vitamins and minerals (Ca, Cl, Mg, P, K, Na, etc.) so you can get them from food :)
I do think filtered water is important because I respect the rule of bioaccumulation--if it kills small things, it's usually bad for big things in that food chain. The disinfectants used to treat tap water are poisonous to us at large doses, so I try not to consume even small doses if I don't have to.