We narrowed our problem to disposal of Plastic Bottles as a very large number of plastic bottles end up clogging landfills and also harming our aquatic life. So we thought that instead of thinking of a new way to dispose or decompose plastic bottles, we come up with a way to reduce the amount of plastic bottles getting disposed of.
First toy that we made was a Flash Light using plastic bottles, sticks, an LED bulb from a broken toy and a battery holder from that same broken toy. Made a simple LED, Battery, Switch circuit and put it inside a body made from plastic bottles and ice cream sticks.
Then we made a car with plastic bottle, bottle caps and motors and batteries. Then we made a SharkBall, a catch-a-ball toy from plastic bottles.