I have just purchased a 24 pack of LiDL own brand energy drink (same mg/g caffeine content as red bull) for £6. And it tastes better than red bull.
Once I had 11 in one night. Not reccomended unless you want to feel intensely sick and end up laughing invoulantarily at things that aren't even funny...
I mostly drink water anyways, so I'd be set with a fridge stockpiled of Energy Drinks. I'd only have to crack one open if I needed to get a quick burst of energy for gaming for a few hours then after that I could crash in bed.