Too tired to function

Y'know when you have one of those days were you're just tired all the time? Yeah? I seem to be having one of those weeks, I have no motivation to do anything, get up, be productive, go to work? Ew, no, i just want to stay in bed. I feel like I'm in such a negative state of mind right now and I don't really know how to shift myself out of it. I think it might be the coffee.. Working for a coffee shop with unlimited coffee is both a blessing and a curse. 
What do you guys do to get out of a sticky situation.. I mean, feeling unmotivated to do anything, right.. What do you guys do to get yourself motivated? I'm interested to know, maybe I could try something!
I went through nine Vanilla Latte's at work once. I don't recommend it.