in this howto i will show you how to build a bong:
Find any type of bottle or can(a 2-liter bottle or 16 oz bottle works fine)
Punch a 1/8 inch (3mm) to 1/4 inch (6mm) hole. About 2 inches (5cm) from the bottom. This hole is where the smoke will enter the bong from your bowl and stem.
Place a tube in the hole at the bottom you've made. This could be a metal pipe, a hollowed out pen tube, or a stem bought at a store or online. Make sure it's at a positive angle, or else your herbs will get wet.
Make sure it's airtight! If it's not completly air tight than your smoke will go out of the holes where it's not supposed to! To fix this use either gum(works best) or tape. To test that its air tight, blow into the mouth peice and put your hand really close to the seal, and blow. If you feel air coming out, it's not airtight.
Attach a bowl to the end of the tube. If you can, pick up an inexpensive glass bowl from your local smoke shop, they will usually run about 5 dollars. You can also roll a cigarette with rolling papers and attach it to the end of the tube. Aluminum foil can be used but it is not recommended. Please check to make sure your bowl material is safe for inhalation before using.
Fill the bong with water, until the tube inside the bottle is completely underwater by at least 1 inch. You can fill it with more, but there will be less smoke in the chamber when you smoke. Make sure you don't put too much water, if you do it will drown your herb!
Load the bowl with your favorite smoking product, cover your clearing hole up with one finger. Light the filled bowl and hit.