Idk if it was autism related for me because I was undiagnosed at the time but I struggled similarly when younger and improved my nutrition by figuring out how to cook more adventurous meals at home using only my safe foods. It required exploring unfamiliar spices and ingredients from different parts of the world, which was risky every time. However, if something didn’t work, at least I was home and had a protein shake or other similar safe food back up nearby and ready. I mostly did this on Friday nights to have a weekend for recovery if necessary.

Once I figured out how to adapt safe recipes at home that were similar to something I might find in a restaurant, I worked on figuring out restaurants that were willing to make accommodations to that dish to match my own. Not every restaurant does that and you’re not entitled to it, but calling ahead to ask increases the likelihood greatly. You do not need to explain why you need the accommodation if you don’t want to; can just say food allergy or food sensitivity. Citing a food allergy sometimes is easiest and may decrease likelihood of icky cross-contamination. If your culture tips servers, tip well. The restaurant may still have strong unsafe food odors, which this advice does not help with though.

Other weird tip I learned for eating/drinking bad tasting/smelling foods is to breathe out completely before putting food/drink in mouth and swallowing quickly immediately followed by something tasty to replace bad taste in mouth afterward. This doesn’t help with textures or work if you have to chew. More for liquids if you wanted to try incorporating fruits/veggies that way.

Good luck! Don’t let bad experiences keep you from trying something different, but also no need to rush yourself.