Plain water is the best for rehydration. Drinks with sugar (natural or otherwise) and salts (gatorade) don't rehydrate like water.

If your mouth feels dry, if your lips feel sticky, if you pinch the back of your hand and your skin stays pinched/peaked more than a few seconds, you are probably still in need of hydratation.

When I had an illness that caused me to be dehydrated often, I would rehydrate by drinking a glass of water every hour. It seemed to work well for me.

I hope you feel better soon.