If you are buying the Gatorade by the bottle it is expensive, however in the powder form it is a lot cheaper. I use G2 which is basically the same as original Gatorade but half the sugar. With original formula, I always diluted with water because I couldn't stand the sweetness.

For use during golfing as an example: I drink one .5 litre bottle of water with one packet of mix before going out. Then drink about another 1 litre of either water or G2 during the 4.5 hour round. (I use that example because it has a typical time window and known amount of exertion for me. Other activities can range from hiking to kayaking to.... and each activity would have different lengths of time, exertion levels and greater variation which means you cannot faithfully predict how much I will need to consume via this forum.)

I don't think you NEED to drink a lot of water during an activity but by taking in a normal amount you might be slightly dehydrated at the end. So what? Your body will stabilize itself by cutting urine output or your natural thirst will tell you to drink more. Either way your not going to be at either extreme.