What do you do when you suddenly wake up very early morning?

Well, the title explained it all. But truly. Since I rarely have this problem, I wonder how you guys actually manage this situation?

Sleep is essential and needed. However, most of the time, you just depend on your biological clock to wake you up just few hours (or minutes!) before the working hours. If things, go wrong, what would you do? Especially if you have a very important meeting. Or maybe cause it is just too early (like 1am) and you just don't wanna be awake and be alone at that time.

What do you do? Please don't say "Play Habbo". Lol.

I work very early shifts (start at 4am) so I sleep during the day (usually 12 noon until 6pm), so thankfully when I wake up, I don't have anything immediate on my mind. If I wake up any earlier, I usually just go back to sleep. The people I work with wake up at 3am and go to sleep at like 8/9pm. I tried that when I started, but couldn't deal with it. It seems like I'm never tired enough to sleep that early, and I hate waking up and having to get ready for work straight away — I never feel like I've had enough sleep and it makes me so miserable when my first thought of the day is 'work.' With my current job, when I wake up, I usually have seven or eight hours to do whatever I want, before I have to start thinking about getting ready for work. I know the hours are quite eccentric and wouldn't suit a lot of people, but they work for me.