Edit: I completely missed the latter half of the OP.

I haven't done much experimentation. I know caffeine calms me down and helps "grease the wheels" in getting my brain to function. Alcohol helps ease my social anxiety and helps me relax and unmask around my close friends.

I haven't found any diet that specifically eases autism symptoms, but meal-prepping when I do have energy does help for the times when I don't.

Original off-topic post below./edit

When I'm not trying to lose weight I just cut sugary drinks out of my diet. My biggest rule is that if I go to the fridge for any reason I must pour myself a tall glass of water and drink that before I get to enjoy whatever snack/drink/meal I went to the fridge for. I don't drink enough water of my own accord, and this helps offset that.

I live alone, so I don't buy any food I don't have a plan to eat. I can't stand food just sitting uneaten. The recipes I've come up with for meals require simple fractions of products I know I can get at the store, so I can, for example, buy exactly enough ingredients to make my favorite stir fry recipe four times and have nothing left over.

When I do try to lose weight, I've found the keto diet has been most effective for me to actually stick to it and enjoy it. Even when I'm not strictly keto, I still stick to keto snacks and drinks, and just let carbs be in my meals. I have very little self-control around snacks that are in my house, but I have plenty of self-control at the store, so I just don't buy unhealthy snacks to have at home. Left to my own devices I can and will eat Girl Scout cookies by the sleeve and drink a 2-Liter of soda in one sitting. When my friends visit for board games and leave their snacks here they will be gone within 24 hours. The recent popularity of seltzer waters like La Croix have been a godsend for sating my soda addiction, since I can get the mouthfeel of soda without the carbs or the carcinogens in "diet" soda.