Cans

You can't close a can, so it carries a certain sense of urgency. You need to drink it before it  spills, you need to drink it before you go anywhere. You can't take it on the bus and you can't leave it around your house because dust will settle into it or a fly might get in there and you wouldn't even be able to see it.
That's another problem with cans, you can't see through them. Someone could slip something in there and you wouldn't even know until you drank it. Hell, they could add a poison, and the poison could change the colour of the drink if it damn well wanted, but you wouldn't know, because it's in a can.

But cans are made out of aluminum, which is pretty sweet. So we'll deal.

(this is why I buy my energy drinks in the big cans, you know, with the tops on them. Not because I need that much energy drink, but because I can close it, and take it on the bus, and take it to work.
I guess I'm not only paying for more energy drink (Which I don't even need) but I'm also paying for the convince of the lid. I guess I'm getting screwed by the corporation.
And it tastes like taurine and ginseng. Delish)