There are lots of debates around biomedical treatment for autistic children. Some parents report that their children can pay attention better, sleep better as the result of diet adjustment and intake of certain nutrition. On the other hand, others stand against the idea to completely cure autism and make autistic children normal. 
Since current research have not shown sufficient evidence to support biomedical treatment for autistic children , we shall separate two components that are often mixed in these discussions.
To treat the symptoms caused by unsuitable nutrition (such as sleep, development, digestion)
To honor and support autistic children to become the best version of themselves they could be
I believe that carefully watch your diet for your ultimate health should be everyone's essential self-care. This “food as medicine” practice has a long history in Chinese Traditional Medicine. Unfortunately, there is still a long way to bring this practice to all. For anyone, fine-tuning your nutrition will make you feel better.
In my educated guess, many autistic children are more sensitive to unsuitable nutrition and/or environmental changes so that their suffering is more obvious. But neuro-typical people show less suffering from an unmonitored diet or unhealthy environment does not mean their performance is not compromised. They simply are not aware of the impact until they are surprised by a disease or decline.
I am not autistic, but I am fully aware that my hearing is ultra-sensitive compared to most people. I use my ability well as a musician and music therapist--I can sense what most people cannot sense. I have learned to use musician earplugs in places like public transportation and Cafe because these environments are too noisy for me and drive me crazy (while for most people, they do not feel it at all).
That shift the paradigm to neurodiversity  is the key. We are all wired differently and this is the beauty of human diversity. What we need to do is to keep learning about our body, our self, our commonality, and uniqueness. Based on understanding and reverence of our unique mind-body, we will live our lives to the fullest.
As resources, I recommend the following books and YouTube Channel.
1. The Survival guide for kids with ASD and their parents, co-authored by parents and a psychologist specialized in ASD.
2. The Reason I Jump: The Inner Voice of a Thirteen-Year-Old Boy with Autism
Author of the book: Naoki Higashida was born in Kimitsu, Japan in 1992. Diagnosed with severe autism when he was five, he subsequently learned to communicate using a handmade alphabet grid and began to write poems and short stories. At the age of thirteen he wrote The Reason I Jump, which was published in Japan in 2007. Its English translation came out in 2013, and it has now been published in more than thirty languages. Higashida has since published several books in Japan, including children’s and picture books, poems, and essays. The subject of an award-winning Japanese television documentary in 2014, he continues to give presentations throughout the country about his experience of autism.
3. Amythest Schaber has a YouTube channel called "Ask an Autistic," where she shares various topics about autism. She is a Métis, Autistic, and multiply disabled writer, public speaker, artist, and activist. they/them.
Schaber, A. (2014, July 30). Ask an autistic #17 - biomedical interventions for autism. Retrieved May 02, 2021, from https://www.youtube.com/watch?v=bPk6sNLfqrU
Lofthouse, N., Hendren, R., Hurt, E., Arnold, L. E., & Butter, E. (2012). A review of complementary and alternative treatments for autism spectrum disorders. Autism Research and Treatment, 2012, 1-21. doi:10.1155/2012/870391
Shute, N. (2010, October 07). Alternative biomedical treatments for autism: How good is the evidence? Retrieved May 02, 2021, from https://www.scientificamerican.com/article/alternative-biomedical-treatments/
Den Houting, J. (2018). Neurodiversity: An insider’s perspective. Autism, 23(2), 271-273. doi:10.1177/1362361318820762