I imagine vault has a high amount of caffeine, yes? Caffeine is horrible at dehydrating you. Seeing as you went on to do P.E., I'm sure you must have been severely dehydrated. I get it sometimes playing rugby and get a lot of the symptoms you listed. It's imperative to drink and eat before taking an energy drink, and then to constantly replenish and hydrate throughout the day. I wouldn't wake up and drink an energy drink, tbh. Not even a cup of coffee. They say now coffee doesn't 'wake you up', but helps level out your caffeine withdrawal from the night. An apple, now that wakes you up!