So you want to turn your plastic bottles and bags into 3D models? The Renegade 3D Pen can help. It is a cool gadget that lets you draw in the air. It lets you print 3D models by recycling your existing plastic items. You can use the ChupaCut plastic bottle shredder to produce tape for Renegade. It is also possible to use regular filaments.
Renegade can use 5 to 7 mm strips cut from PET plastic bottles, plastic bags, or other items. Seems like a great way to get started with sustainable 3D printing. More info is available here.