Back 10 years ago when I was cycling alot and racing MTB, I tried beet juice and beet juice powder as it was supposed to help performance. If I remember correctly, I tried MRM beet powder as well as a couple liquid concentrates. Sorry, I can't remember the names now. I'm not sure I noticed any performance gain, maybe some. But I do know others that swore by it.
I've used superbeets stuff off and on for a while. It's not something you take and your feel like a hero. It helps with circulation and getting oxygen to your cells. I've used it to ride and run longer. I found it when I was doing 3 hour MTB races. I can't say how much it helped, but if you plan on riding and race pace for 3 hours, you try some things. I podiumed in those races, so maybe it worked.
*Podium.... I used the same thing in my smoothies a while back. Can't definitively say whether I could tell a difference or not. I was also taking a Nitric Oxide booster, which has a similar effect. That was one supplement that you could definitely feel the effects of.