My friend Janet bought a bunch of these at a dollar store for her Girl Scouts to decorate. Specifically, she wanted to know what would stick to it. She was planning to have them draw with permanent markers, but wanted to know if I had thoughts about how else they could be decorated. Rather than guess, I decided to experiment.
I started with rubber stamps. As I suspected, regular ink rubbed right off, but Staz-On ink worked well. It smears if you touch it right away, but after drying for 30 seconds, it's fairly permanent. (Meaning, you can scratch it off if you try, but it doesn't just rub off.) I tried a variety of pens to color in the stamps. None were great, but Sharpies worked best.
I tried paint next. I thought it would fail and it did. I didn't even photograph it. Just imagine paint not sticking to plastic. Stickers, however, were great. They adhered easily and held firm.
My project looks a bit crazy since every side is decorated with different materials that don't really go together, so it won't be on display. But it will be fine for holding garage odds and ends. It was certainly fun to experiment. I'm looking forward to seeing what the Girl Scouts make!