A study found that sports drinks work because they activate the pleasure center of your brain. You don't even have to drink them, just swishing some around in your mouth and spitting it out has the same effect.
However, motor oil will not "unlock the power" like the bottle says.
The carbohydrates in the drink stimulate receptors in your mouth that then send your brain messages that things are all totally cool. Your brain, in turn, becomes more active in the pleasure center, allowing you to enjoy feeling the burn far longer than some idiot without a sugary drink. It also stimulates the part of your brain in charge of movement control. So not only will you be content while kicking your water-drinking opponent's ass, you'll actually be kicking it harder.
At some point, we've all at least been near a television while a women's tennis match was on and (even if briefly) mistaken the sounds for porn. Particularly the noises Monica Seles used to make. Grunting, and sometimes almost screaming, is common place for many male and female athletes and while it might seen ridiculous and distracting, according to one study, grunting in tennis actually helps those players win.
But the right clothes make you famous.
Now as intuitive as it may seem that grunting would help put more muscle into a swing (like karate guys screaming "HIYAA!!" when they hit you), that's not what the study suggested.
Instead, the grunt is effective because it can disorient the opponent. Even when a non-grunting tennis player is used to playing someone who makes a lot of noise, each and every grunt in every match actively affects the tennis player's ability to return the ball. This is likely a result of the shock the sound causes on the opponent, making it harder for him/her to perceive where the ball is at any given time. It also, drastically slows the reaction time of someone trying to return a serve from a heavy grunter; after a player grunts, the ball will travel on average two feet further before being returned than it would have with no noise at all.
So if you like to make noise on the court, it might not be winning you any friends but it very well could win you the game. Isn't that what's really important? And you know what would really give you an advantage: combining grunting with the singing thing earlier. Time to start memorizing some Nickelback lyrics, baby!
For more bizarre determining factors, check out 7 Life Altering Decisions Made For You (Before Your Birth) and 6 Ridiculous Factors That Determine Who Wins The Super Bowl.