Water becomes cold on mixing energy drink
Well, the solution enthalpy of sugars is positive.
I found these numbers on the internet


$\ce{C12H22O11}$ (sugar(sucrose)) : 5.4 kJ/mol
$\ce{C6H12O6}$ (glucose) : 11 kJ/mol
$\ce{C6H12O6·H2O}$ (glucose monohydrate) : 19 kJ/mol


So if your "energy drink" is a dry powder (and not a readymade drink in an aluminum can), this could explain your observation.

You should however put a thermometer into your experiment, and get us some numbers. As is, my above is just another piece of guesswork.