Next step is to find a place where you can get a hell load of dry sand (the finer, the better). Take the bottles, fill them with sand, seal and then paste them with a mixture made of earth, clay, sawdust and a little cement to provide additional strength and durability. The following video shows how to fill the bottle. Now you are all set.
The term brick refers to small units of building material, often made from fired clay and secured with mortar, a bonding agent comprising of cement, sand, and water. Long a popular material, brick retains heat, withstands corrosion, and resists fire.