Soda bottles, especially the 2-liter variety, can be repurposed into many things. One such project that's easy enough for children to help with is a birdhouse. You'll be keeping trash out of the landfill by making this project, and also providing housing for neighbourhood birds in the process. You'll also give yourself and your family something to look forward to each day, watching a bird family grow in your back yard.
Remove the label from the soda bottle. Wash out the bottle with a little dish soap and water. Rinse it by filling the bottle halfway with fresh water, replacing the cap, then shaking the bottle vigorously. Remove the cap and pour out the water. Dry the outside of the bottle and allow the inside to dry.
Poke a small hole near the bottom of the bottle with your craft knife. Poke another hole at the same height on the opposite side of the bottle. Tape one end of the twine to the end of a foot-long piece of wire. A straightened wire coathanger will do if you don't have any other wire handy. Push the wire and twine through one hole in the bottle and out the opposite hole. Remove the tape and hold onto the twine end as you remove the wire from the bottle. Pull one end of the twine until it's approximately equal length on either side of the bottle. The twine will be tied to a tree branch later.
Hold the bottle upside down and note that it will hang upside down when the project is completed. Poke a hole with the tip of your craft knife about three inches up the side of the upside-down bottle, not including the neck. Poke a hole at the same height on the opposite side of the bottle. Push a chopstick through one hole and out the other, leaving an equal amount showing out either side.
Cut a round hole on each side approximately 3/4" above the chopstick perch. The holes should be about an inch wide and as smooth as possible. Remove any loose or sharp bits of plastic.
Poke another hole with the tip of your craft knife several more inches up the bottle, but not directly above one of the other holes. Poke another hole on the opposite side at the same height. Push another chopstick through as in Step 3. Create two more inch-wide entry holes as you did in Step 4.
Paint or spray-paint the outside of the plastic bottle. Allow to dry completely. Hang the bottle birdhouse outside from a tree branch by tying the ends of the twine over the top of a tree branch. Be sure the knot is strong and won't pull apart.
The birdhouse should hang at least 5 feet off the ground, ideally, to keep it out of reach of animals and small children. One-litre bottles could also be made into birdhouses.
Do not make birdhouses from bottles that held harsh chemicals such as bleach. An adult should handle the cutting portions of this project.