I've used this Energy and Focus drink mix from Wilderness Athlete before. It seems to give me the same boost as my go-to Rockstar "Recovery" energy drink and keeps me on task in the afternoon at work.
As far as something to use to help sustain energy while racing I use Ryno Power products. Their Hydration Fuel mix goes in my hydration pack and I take the Endurance and Electrolyte capsules before my races. It has helped me a lot sustaining energy and avoiding cramps through 2 to 2-1/2 hr XC races. The recovery after the races seems to be faster when I use this stuff too.