The bleach option is often marketed online as "Miracle Mineral Solution," or MMS. Videos promoting it can be found on YouTube and have been watched millions of times.
In addition to the videos, proponents of MMS sell books promoting their "cure" and also market the chemicals.
But the U.S. Food and Drug Administration says this bleach, chlorine dioxide, can cause "serious harm" and calls MMS a "potentially dangerous product."
"The FDA has received several reports of health injuries from consumers using this product, including severe nausea, vomiting, and life-threatening low blood pressure from dehydration," the agency said in a 2010 health warning. "Consumers who have MMS should stop using it immediately and throw it away."
Still, nine years after the warning, parents continue to give it to their children - orally, through enemas, and in baths.
The results are often disastrous, according to two moms of autistic children who have gone undercover in private Facebook groups.
"My son is constantly making a gasping sound," posted one Kansas mother who claimed to treat her adult son with chlorine dioxide, according to screenshots shared by Melissa Eaton and Amanda Seigler, NBC reported.
A Canadian mom wrote about her 2-year-old's unwillingness to drink the bleach mixture. "He won't open his mouth ... He screams. Spits. Flips over."