How to drain a waterbed without using a pump?

waterbed is in a second floor bedroom that does have a window.

Hose out the window. Suck on it until water flows. Voila.

Siphon. FILL a hose with water, put one end in the bed, and the other on the ground at a lower level. Put the bed end in first, Hold the other end above the bed, capped, until you get the end out the window. Then lower, and uncap. You can get caps at the hardware store, garden store, or at places like Home Depot. The water will flow out of its own accord. Since you are on the second floor, you should put the other end on the ground, such as in the gutter of the street. If it's your own yard down below, it's not so much of a problem, but you need to make sure you don't put water in the neighbor's yard or home.

stab it with a knife

thats so hard to do!!
id just leave it in the bathtub

that's crazy! use a pump

siphon it out with some hose hanging out the window

Siphone with a garden hose, hope your not in a hurry!

If you don't have the connections already get them at your local hardware store and use a water hose that you've filled with water.

just sleep on it.

Stick a garden hose down into the matress. Run the hose out the window to the ground. Carefully (that water is nasty!) suck on the end of the hose or use a shop-vac until you get a flow. The bed will drain in an hour or so. If the garden hose won't go in, then go buy a cheap one and cut the end off.

ALWAYS unplug your waterbed heater before draining or filling your waterbed.
Attach your garden hose onto an outside faucet (the hose can go up through an open window).

VERY IMPORTANT - Turn on the water for fifteen seconds. This pushes the air in the garden hose into your bed so you can create a continuous water siphon.

Turn off the water. Disconnect the hose from the faucet and let it drop to the ground.

As long as the end of the hose is lower than your waterbed, gravity will siphon the water out.