You've probably seen the ridiculous claims on supplements packaging before. Stuff like, "Improves Endurance 45%" or "Accelerates Recovery!"
I've been training and racing for the better part of 12 years. I've seen a lot of garbage, even used it myself when I was younger. But now, I take a multivitamin and an iron supplement -- that's it. Of course, I might consume carbohydrate before, during, and after exercise. And I occasionally use whey protein with a carbohydrate source for a quick and easy recovery shake. I also enjoy a good cup of coffee.
But while supplement companies keep trying to pump you full of their dishonesty and products, I urge you to take the time to evaluate their claims and the research as a whole. The first source I use when I consider a supplement is the Australian Institute of Sport's website. Here you can find their fact sheets on popular supplements as well as their classifications. You'll notice all the Group A supplements are the no-nonsense, heavy hitters -- carbohydrate, whey, caffeine, creatine (in specific circumstances), electrolytes, iron, multi-vitamins, and so on.
There is no (safe or legal) magic pill that will boost your VO2max or improve lactate clearance. Be wary of claims like these.