You probably shouldn't shoplift it, either: Stores already factor losses/shrink into the price, so unless an item gets shoplifted so often (e.g. through a coordinated effort) that stores just stop stocking it, all that will actually happen is (1) the store will just buy more to restock; (2) the act of shoplifting provides data about demand for the product; (3) you still promote brand recognition.

Shoplifting Monster is still preferable to buying it, but the real best thing to do is to either switch to a different energy drink brand, or perhaps for your own wellbeing to cut out energy drinks entirely.