I voted cans. They're in the vending machines. And I like to buy an occasional soda from the machine. They don't have the best flavor though.
i drink from reusable glasses when i can. when i have to use a vending machine i get a can because we have no plastic recycling facilites here, only metal. plus it's usually more carbonated and bubbly. i NEVER buy bottled water anymore. i carry my reusable bottle, or, on days when i really want to raise eyebrows, my leather wineskin.
I like bottles. Cups would be a close second. I try to steer away from cans since they just create more trash than is necessary.
just take them to be recycled. aluminum is way more renewable than plastic (i'm assuming you mean plastic bottles from a machine) and also, let's not forget about the huge amounts of plastic floating around our oceans, and the amount of oil it takes to get plastic to the consumer. (don't get mad, this is all based on assumption)
I prefer a glass or cup. If I drink a beer (which is very rarely these days), I prefer it in a glass or plastic cup, depending where I'm at or what event I'm at.