To stay awake, I find VK-blue to be the best thing. However, you'll also be pissed, so probably not the best idea with essays to write
To wake yourself up in the morning, sugar (in the form of coke/lucozade etc.) is much better (to me...) than caffeine, though a cup (the mug I use is larger than 2 standard mugs!) of coffee in the morning is always good.