I have used Gatorade mixed 50/50 or 40/60, 30/70 (less Gatorade - more water) when I couldn't get Rocket to drink and he was obvioously dehydrated. Vet said it was ok to do this to get him to drink, but not to keep adding Gatorade, just add water to the bowl as he empties it. Rocket has a sweet tooth, so he liked the flavor and the sweetness. Only one bowl of water this way - don't keep giving Gatorade over time. A little is ok, too much is not good.
Make sure he actually is dehydrated before you do this.
Edited to add - I was typing this while you and Doggfather were responding above. Doggfather knows best - forget the Gatorade for now.