I spent the first 12 years of my first child's life trying to make it possible for him to sleep decently. Off the top identity head:

ASD kids are picky. Try to keep foods on hand that are healthy and that the kid likes. Let them eat what they want from what is on hand.

Hey them a good multivitamin. Disney Princess Gummy vitamins worked well for my kids.

Make sure they get outside every single day for some physical activity. You may have to work at making sure this happens at the right time of day as well.

Kids need to be both physically tired and mentally tired to sleep. ASD kids have trouble getting the mental stimulation they need. Video tapes and video games sometimes serve them well.

Don't substitute physical exhaustion alone for physical tiredness plus mental tiredness. This can cause night terrors, where they wake up screaming after an hour.

Be accommodating of their weird preferences as much as possible. My oldest slept all kinds of weird places when he was little.

I have had a parenting blog in the past. I have fantasies I will eventually get back to that.

Best.