Most energy drinks taste too syrupy to me to drink while riding, but I've gotten to be a big fan of Recoverite.
I used to feel a little run down the day after a harder training day, but the stuff helped me noticeably. My can is down to the last scoop and I'm doing a solo-century tomorrow, so I guess on Sunday morning, I'll find out if it's the Recoverite, or just my body getting better at recovering.