Pr Peronnet answers you
"The short answer is yes, because their main ingredient is water, and to be hydrated you need water. But the long answer is that these drinks not only contain water, but also minerals and sugar, and this is not always appropriate to remain hydrated.
These drinks contain minerals and sugar because during prolonged exercise this can be beneficial because the loss of minerals is important and sugar can improve endurance performance. But for a regular fitness exercise session, mineral loss is small, and adding sugar may add unwarranted calories and it’s probably not optimal. For this reason the idea that sports drinks are efficient to stay hydrated in all circumstances is probably a myth."