Can I get the same amount of hydration if I mix water with kool aid?

Yes. The potential difference in the amount of "hydration" between pure water and kool aid is very small. Depending on sweetener you may get a little extra sugar, but that does not substantially effect the amount of water you get. If you are really sweating up a storm this would not be a good "hydration" solution as it does not contain enough salts to replace losses.