maybe off beat here

I have access to lots of 2 Liter pop bottles here. They just go to recyling for the guy what makes plastic picnic tables so I was wondering if they [if you] have any ideas of something I could use them for with the roots ....planters etc, or water devices ...I take from neighborhood maybe 20 a week to recycle...suggestions? Rather than just give away maybne you have some ideas for uses? Thanks.