I tried to re-use plastic petri dishes, after initially discarding the contents (this was done outdoors), I washed in regular dish soap, then soaked in a 10% bleach solution for 10 minutes, then dunked in sterile water to rinse the bleach, then submerged in Peroxide for 2 minutes, they were pulled out of the peroxide in front of my flow hood. 21/25 of these "cleaned" plates exhibited signs of bacterial contamination right on the edges of the dish in the corners, underneath the agar I poured. 4/25 were actually clean. Were I to try again, I would increase the concentration of the bleach solution to 15%, and leave them in there longer.
That being said, I will never try again.
I bought some 60mm high borosilicate glass petri dishes I can just bake in the oven or pressure cook to sterilize. More expensive initially, but less wasteful in the long run, less expensive too (after a good number of reuses). the amount of time / resources I will save in sterilization is worth the investment in my opinion. I don't like single use plastics - even if they are "recyclable". Even the grow bags bother me a little. I am looking for appropriately sized PP5 containers for fruiting blocks that I can modify/utilize and REUSE instead of grow bags.