Are sports-drinks necessarily? Do they improve performance?

Staying hydrated during a workout is important, but unless you’ll be sweating it out for 90 minutes or more, don’t drink anything but water. The body starts running out of electrolytes or glucose only after 90 minutes of constant exercise (this might slightly change depending on intensity and body type).

So a sports drink will only add unnecessary calories to your diet if you drink it during your usual 1 hr workout. A sports drink is sensible to take when engaged in longer workouts (longer than 90minutes): its electrolytes help you sweat more efficiently so you retain precious water.

After a workout you need to replace glucose and supply the body with protein for muscle repair.