Gatorade and other sports drinks are actually hypotonic solutions. how do these drinks rehydrate their users?

They cause water to enter the cells, which restores hydration

Hypotonic solutions will have lower osmotic pressure compared to the water in our body. This will make the water to pass semipermeable membrane in our cells and make us hydrated again.

This type of solutions are really useful after doing heavy activities that cost us a lot of ions from our sweats