I don't do these things now, but as a child I used to suck coal. My dad was a coal miner and we had a shed full of the stuff. I also used to suck wet sponges and flannels.
My eldest brother who is also autistic but needs full time care used to eat poo if you didnt catch him in time. This happened till he was toilet trained at about 9.
My eldest son who has an aspergers diagnosis still chews things he shouldn't and he's 19. He chews mainly plastic and thin bits of metal, so bottle tops, coat hangers, whole pens etc. His room is littered with plastic fragments.
As a young child he would chews through the cuffs of his clothes.
I have quite bad TMJ disorder as I bite down so much. I'm wondering if this is possibily a stim too.