I do not use energy drinks (except coffee - get off my lawn!), but my daughter swears by them. Tried one and it made me jittery and fidgety. Is this generational? Seems like younger people don't need them but use them more than older folks (or at least these energy drinks are target marketed to younger people). I don't see a lot of energy drink ads directed to the over 50 crowd. What are your preferences, thoughts? Do these work or are they a gimmicky waste of money?