For the past decade or so, gas stations have been stocked with energy drinks. I should say that they are energy loan sharks. For regular users, eventually the "kick" that you do feel is not as good as the way you feel all the time when you are off those suckers. Basically, consumers are taking a sugar and caffeine bomb to their systems. Some contain beneficial amino acids and B-vitamins but the HARM far outweighs the benefit in my opinion. In addition, like soda, many contain phosphoric acid, which eats away at calcium needed for healthy bones which can lead to increased risk of stress fractures.
Back at Clemson, I was a heavy user of these energy loan sharks so I am qualified to make a review. I actually think Red Bull is one of the better ones because it only contains 80 mg. of caffeine and does not contain high fructose corn syrup. I get a negative reaction to taurine nowadays so I won't get any benefit from it now but it's been somewhat effective for me in the past when I needed a temporary kick. In 2009, I consumed a Red Bull prior to a few of my 59.9 attempts and came within 1.23 seconds going solo. Marathoner Brian Sell drinks a mixture of Gatorade and Red Bull during the race and made the 2008 Olympic team. I tried it myself at Mercedes 2009 and scored a massive PR. Did it help? Maybe a tiny bit but I credit my training and preparation. I will NOT go as far as recommending it to others and do NOT consume it on a regular basis.
As for some of the others such as NOS, Amp, Full Throttle, Rock Star etc., they might as well carry a Yuck symbol because it's basically poison to the body. In addition to the ill-effects listed above, I found that I got nasty GI issues as well and did a fair amount of running to the bathroom.
Heavy long-term use of sugar and caffeine is one of the WORST things that you can do to your adrenal glands. Without a doubt, it was a major contributing factor to my collapse. My doctor says that 60-80% of adults have sub-optimal adrenal function. To clarify, sub-optimal does NOT lead to crippling fatigue. The average person may only lose 5% of their performance capability. For a sedentary person, it's not even noticeable but for an athlete, it's huge. It marks the difference in a world record level performance and the fringe of world class. For a runner of my caliber, it represents about 20 seconds per mile and I will certainly notice.
I have also experimented with other energy drinks that are non-carbonated and contain little sugar, most notably, FRS Healthy Energy. My review is pretty much the same. It may give you a small boost when you need one in a race but it's not to be used regularly.
As for Gu, gels and Sport Beans, I have used them in both races and training with mixed results. I credit Sport Beans for helping me get to the finish in my first marathon. I've also had GI issues when taking them so as of now, it's too much of a risk. My pace actually slowed by 10 seconds in Columbus AFTER taking a gel. Did it hurt me or was it just the curse of Mile 10? During 3M, my only energy sources were Gatorade and water and I'd say it worked out quite well. Others swear by their chosen energy source so I'll just say, to each their own and do what works for you.
My plan for Mercedes since it is a full rather than a half is to carry small amounts of 2-3 different energy sources to be considered as I approach the wall but if I don't feel I need it, I won't take it. I will hydrate with water and Gatorade at set intervals.