Are you more interested in 1) measuring the amount of caffeine in a drink, or 2) creating a decaffeinated version of an existing energy drink?
If you are interested in 1) measuring the amount of caffeine in a drink, existing caffeine measurement methods for tea/coffee will likely work the same. https://chem.libretexts.org/Bookshelves ... Experiment
) seems like a good start. Be sure to use a fume hood and proper protective equipment. For your reference, here is the MSDS for methylene chloride (one of the solvents used, which is hazardous): https://www.fishersci.com/msdsproxy%3Fp ... oductDescr
If you are trying to 2) create a decaffeinated version of an existing energy drink, this will be much more difficult. In tea leaves and coffee beans, caffeine is removed using supercritical (high-temp, high-temperature) CO2 to dissolve caffeine, before the drink is actually made. If you're working with the finished-drink already, the method for 1) would leave your drink toxic. You'll have to find an existing decaf version, or perhaps water would be a good alternative
Hope that helps. Let us know if you have additional questions.
Renee and Charles