I've been saving my Juicy Juice plastic bottles so that I can make something out of them. For this experiment I cleaned the bottle, using Goo Gone to remove the sticky part that held the label on. Next I cut off the top of the bottle. I'm saving that part for another experiment. Then I hole punched around the top of the bottom half. Next take a tapestry needle and make a blanket stitch through each hole. Round 1: Single crochet one to three times in each blanket stitch (just use your best judgement for the amount of times). Round 2: single crochet in every stitch. Round 3 and up: Double crochet in each stitch.
I plan on crocheting the same height as the plastic bottle. Then I am going to make shells (I don't know what they are called) to finish the top. Then I'll weave a ribbon through to make a drawstring. This would make a good small project bag or yarn holder.