I'm personally a big advocate of repetition before big tests. By this I mean that for a period of time (say, a week) before the test, do the exact same thing every day that you plan to do on test day. So, for example, if you have a 9:00am test time, make sure that you eat and drink (whatever is a normal breakfast for you) before that time and be sitting at a desk somewhere ready to exercise your brain (e.g., start doing practice problems or a practice CAT) right at 9:00. Your body gets into rhythms, so by getting into a routine in advance of test day, you ensure that no unknown variable will taint your performance.
This is especially true when it comes to coffee and/or energy drinks. I used to do the same thing before big exams: buy a red bull to drink half way through. That is a fine strategy
if you are used to it. For someone that does not normally drink coffee or red bull, these drinks will just make you jittery and make your mind race or jump around more than you're used to. So, my advice is, if you start every day with a strong cup of coffee, do the same on test day. If not, don't. If you use red bull (or 5 hour energy) to reinvigorate yourself fairly often, then it will probably be beneficial on test day. If it's not part of your normal diet, don't switch it up on game day.
In short, test day is not the time to experiment.