I've seen some gorgeous photos of garlands made from transformed water bottles online and decided to try it with a group of children. It's best to use the lightest weight bottles that you can find so that they are easier to cut. I used scissors to cut off the bottom couple of inches. I cut the sides into strips to mimic flower petals. We tried painting some of the flowers with acrylic paint, but it prevented the light from shining through. Most of the bottles pictured are decorated with permanent markers. I had read that bottles could be joined together with a glue gun, but I was not successful in making them stick together. At first I couldn't figure out how to string them with straws between the flowers so that they stayed separated. I came up with the idea of stringing circles of heavy paper in between the straws and the bottle caps. You can see this in the photos.
If you can find a place to hang them with a good light source they cast beautiful reflections.