'isotonic' or electrolyte drinks are only of use to genuine endurance athletes (marathon, triathlon etc), and those with prolongued diahorea (eeew
1/3 of the water we need, we get from our food. There was a trend towards pre-empting your thirst mechanism and drinking water 'habitualy'. As with everything, contradictory research eventualy comes along, and this subject is no different, and much new info points towards what 'Sprite' have always said- 'obey your thirst'.
I am always in favour of common sense. Every mammal on earth has the sensation of thirst. We are the only mammal on earth that can do physiological hydration studies, relying on your natural insticts will not do you any harm in relation to ingesting water.