In the last few weeks I've given up the whole sports drink / high energy drink /caffeine thing. Used to guzzle 3-4 energy drinks before/during a match, some with caffeine eg. Gator, Relentless, Monster, would have a double expresso with a couple of sugars 30 mins before the match to perk me up etc.
It just all played yo-yo with my moods and energy levels. Would end up psyched, aggressive, super tense with too much energy in the first match and then super flat in any match going towards the 2-3 hour point. I just don't believe that any of that stuff or too many stimulants is good for you (well, it wasn't good for me). At times, I was doing a good impression of someone on PEDs.
Now I just try and prepare normally. Have a good nights sleep, healthy meal, a mixed orange cordial during the match and occasionally, a electrolyte drink as I seem to suspectible to muscle cramps in the 2nd match of tourneys for some reason. Could probably achieve the same effect with table salt and water.