Someone who isn't me told me it's better to bang your head against the vending machine.
You still get the same effects as the wall, but if you get lucky, you may actually get a free soda out of the experience too.
LOL
Reminds of time I was spending night in a bus station waiting for a bus, out of money and rather hungry, I saw some teenager try to buy a twizzler, which got stuck in the vending machine of course. But then he starts rocking it!
I jumped up and yelled "Don't do that, it will tip over on you! Here, look out."
He stepped out of the way, and I started slamming it against the soda machine (sideways, so on risk of tipping) After couple seconds of that, the twizzler didn't come out, but about 7 other items did!
So he took half, gave half to me, and bought second twizzler, to get both. Cuz he just really wanted that.
Bang your head?
http://www.youtube.com/watch?v=KtZ7o-UhNCI