I'm allergic to polyester and most anything made of plastic. I get painful open sores, and hideously itchy. It is difficult to find clothes at best.
Plastic is snuck in more shit than you'd think. Often unlabelled. More than one pair of pants/shorts I've had to ditch/edit because the pockets were polyester or nylon in a "100% cotton" garment. Drawstrings are bad for this, too. And waistbands.

Seems to be weirdly common to be adverse to plastic-based fabrics in autistic communities.

I most often wear:

cotton/linen/canvas/denim
rayon/bamboo (plant based, do need to be a bit careful because people fake it, very loose "swishy" fabric)
hemp
real leather ("vegan leather" is literally plastic and i will fight people greenwashing calling it "vegan" and not the awful pleather it is.) (very difficult to find coats without nylon linings though.)

Cotton or anything natural! The idea of my clothes being made of plastic fibers which then enter the water supply or sit in a landfill bothers me. This applies to sheets, towels, etc. My skin also reacts poorly to synthetic fibers.

I recently got underwear made of 46% pima cotton, 46% modal and 8% elastane. Feels very soft and smooth, should last a long time, can recommend.

Wol. Soft kinds like merino. It's comfortable and great at regulating body temperature. It's also great for wearing underneath other clothes in the winter.

For me, the fabrics i like are:

• Wool, especially merino
• Linen
• Hemp
• Raw denim

Cotton I'm kinda neutral on, I dislike polyester and most synthetics.

I think you’re more likely to get nice soft clothes from blends, like cotton/hemp or from “Pima” cotton. They may be more expensive but can last pretty long if you follow the tag instructions

I like finely woven fabrics, as I feel like they trigger the least amount of sensory input.

I've got a bedsheet, which is "cotton with a satin weave" and I like that a lot.

Side-note: I believe, it's a thing that certain autists are really particular about the kind of fabrics they like, whereas others just want less sensory input. You might get both kinds of respomses...

Not a Fabric but Hiking pants, they are light and strechy. And for hoodies: only the Cotton ones with a Zipper in the Front. Might be more of a Heat regulation Issue for Me.

cotton, wool, leather, modal and denim for me. found a tshirt i liked and just order 10 in the same color online when they wear out. same for jeans, socks, underwear and hoodies. rather dress like an npc than decide how annoying i'll accept my clothes being day to day. leather boots, havent owned sneakers in 15 yrs. leather jacket for cool weather. merino wool sweaters and a long heavy wool coat for thundersnow season.

modal beats out cotton sheets to me, but unblended cotton is still pretty comfy. layers of merino wool blankets. finally managed to get leather furniture this winter and my livingroom is usable even when im having a bad day.

also ereaders and stone paper. after gritting my teeth and feeling gross because everything is written on dry scratchy hateful paper. being able to read or just write down a quick note comfortably was kinda life changing.

Do not buy online but IRL and it will be better.

I recently got a pair of pants that are stretchy and I've been addicted to them. I didn't know pants could feel this comfortable. They say they are 65% viscose, 30% nylon, and 5% spandex. I have a hard time wearing anything else now.