I’m part of the autistic spectrum (diagnosed as Asperger’s, but apparently that term has possible roots in Nazism and “racial superiority”, yikes!), and I found that going outside and taking a walk outside always helped me calm down. I remember whenever I got upset as a child and overreacted, the teacher would take me for a walk around the school, and I always felt better afterwards. I also liked eating my favourite snack to calm down, though that might just be because I like snacks.

Just my two cents. I don’t experience too many of the negative “symptoms” of autism anymore nowadays, but I hope you (or somebody else) finds this helpful!