actually, there is rather a lot of research into diet and autism that suggests that sugar has an effect on them.
"Among practitioners familiar with autism, there is strong consensus that modifying the diet and the gastrointestinal system sets the stage for the success of other treatments, and therefore should come first.
Parents have found that, by closely regulating their child's diet, they can observe improvement, and that when dietary constraints are relaxed, the child often worsens. The recognition in recent years of a gut-immune-system-brain axis of pathology further supports this priority.
Food additives can be a particular problem for autistic subjects. Although many of the worst offenders have been banned, others remain in the food supply. Two organizations, critical of irresponsible food additives, that publish useful information in this area are the Center for Science in the Public Interest and the Feingold Association.
Artificial coloring agents can have carcinogenic or mutagenic effects. Simple sugars and artificial sweeteners have adverse behavioral effects in some children. Lab tests (urine organic acids ) reveal abnormal carbohydrate chemistry in most autistic children. Baker urges the parent to test the sugar-avoidance diet by tapering off slowly over three weeks (to avoid withdrawal symptoms), then reintroducing sugar for five days, watching the results. Whether or not the child has a strong adverse reaction to sugar reintroduction, Baker advises sugar in the diet be decreased because it is food for many potentially harmful intestinal dwellers.
For ASD children unusually food sensitive, the Feingold Diet is likely to be highly beneficial) by systematically excluding additives, colorings, salicylates, and preservatives. This and other more restrictive diets for integrative management of ADHD (attention deficit hyperactivity disorder) were previously reviewed. Baker has published a list of additives least likely to affect ASD subjects."
Food affecting behaviour is being very well researched.
I know what I see in my children.
I don't really care for being told that I don't see what I see.
I know not me personally singled out 
but being part of the group saying that they see it and being told it's not real.
It's real.