Most of the well-known energy drinks rely heavily on B-vitamins for their energy source, not just on caffeine, because B-vitamins have a very energy-inducing effect. So, you could look for some caffeine-free vitamin-heavy energy drinks. Taking B-vitamin pills won't work as quickly, but would work over time. However, at least in my experience with B-vitamins, they're more likely to keep you awake at night if taken later, so I'd use them for morning study sessions but not drink a vitamin-laden energy drink at 9pm to try to get 3 hours of study time in before midnight. Basically, vitamins – most of the B's and also D vitamin, if you're deficient in D like much of America – can help make sure you're realizing your full healthy, natural potential. However, vitamins won't make you able to be studying till 1am after getting up at 5am – they're not a wonder drug, just make sure you're at healthy condition. 🙂 Vitamins + sleep = awake and focused, but they rely on health in general, and sleep is part of health in general.
If you can't find any caffeine-free, vitamin-heavy (specifically B-vitamins) energy drinks, then taking B-complex (and D) vitamins first thing in the morning can help with awakeness and alertness, but I'd suggest morning study sessions. Do something like take the vitamins, go take a shower, and then they'll start to be getting in your system by the time your shower is done.
Tea is nice too, but often has caffeine – not sure if that level of caffeine would affect you or not. If some caffeine is OK just not too much, you might look into GFuel – my boyfriend really likes GFuel, and it's much higher energy than caffeine, but it does have caffeine in it.