A battery is made of three main parts: a cathode, an anode and an electrolyte. A simple battery can be made using just a can of soda, a cup and a small piece of copper. The soda acts as the electrolyte, the copper the cathode and the can the anode.
To make this simple version of a battery, you first need to open the can of soda and pour the contents into the cup. The cup of soda plays the role of the electrolyte in the battery. For the anode and the cathode, a copper strip and an aluminum strip are used. A copper strip can be obtained from any local hardware store. For the purposes of this project, you'll only need a 2- to 3-inch strip. The aluminum strip can conveniently be obtained from the can of soda. You can cut a strip out of the side of the can with a pair of scissors, but you want to be careful, as the fresh cut metal will be sharp.
Alternatively, aluminum strips can also be obtained at any local hardware store. You need to bend both of the strips so that they can be set on the rim of the cup. Place the bent strips on opposite sides of the can, with one end of each strip slightly dipping into the soda. You can connect alligator clips to each strip and test the battery using a voltage meter. The battery should produce around 3/4 of a volt.