What about crafty type activities?
Modelling clay.
Building with matchsticks or a model kit.
Spraying shaving cream over the kitchen table and ‘finger painting’ with it.
Painting
Kinetic sand
Making bread (kneading dough)
Cooking

Agree with the colouring in suggestions. Perhaps some construction type activity – lego or blocks. Or maybe a puzzle of some sort such as a jigsaw puzzle.

Every person is different and will enjoy some things that others don’t, or hate things others love etc. Do you know much about this person and what they do enjoy or don’t enjoy? Colouring as one person said sounds good, if they are able to sit for long enough (depends if they are interested in it). Video games are fun for any age. Gardening, going to the zoo, anything that doesn’t require hearing (like a movie without subtitles).

mindful colouring is good for at home. going out look at places that are quiet and don’t have any triggers. bowling can be good. otherwise swimming is also great.

I took a boy fishing who is austisic he enjoyed the company the most showing interest is very important.

It all depends how reactive he is and what his triggers are. I recently found out that some cinemas have low sensory sessions for autism sufferers. And supermarkets also have a similar thing