cheapest and easiest way for me was menthol crystals. amazon has them. use a old 30ml juice bottle that you've emptied. fill with half crystals. fill completely with PG or VG (I've found pg works better, but neither here nor there) and properly shake. let sit overnight and shake again. you now have a menthol concentrate. couple drops of this into any juice will give you a wonderful, icy kick. start low and increase as you like. I do three or four drops per 10ml. its natural and the more you add the more hardcore it gets. one bottle of concentrate should last you forever. I prefer crystals because I know they are natural. good luck but truly, don't over think it. its easy!