Crystal Light has a bunch of different flavors in the sugar--free singles now.  The old 2-quart tubs were nice, but the singles are the greatest thing since sliced bread for flavored drinks while camping.  No heavy sugar to lug around either.

What I like best is being able to mix and match since you need 2 singles per quart nalgene.  Raspberry Lemonade and Iced Tea is a good combo, for one.

Cryustal Light also has a version that's similar to Propel in that it has electrolytes (good) but no sugar which you really shouldn't need for energy if you are eating properly.

Ironically, the more convenient these drink mixes have gotten, the less I'm using them.  Since I quit treating my water with the tablets except for when the quality seems questionable, the water tastes too good to mess up with flavors most of the time.  I'm down to 1 quart a day of flavored stuff and the rest is straight water.