Children with ASD are sometimes picky eaters. This may be in part because they have felt the effects of foods that don't work with their body. It may be a sensory issue as well. Children with ASD may be hyposensitive to textures or hypersensitive. What tastes good to you and I may not be the same to a child with ASD.
Children with ASD have been known to benefit from a gluten-free and caseine-free diet. Vitamin supplements have also been known to be effective with ASD children in eliminating behavior problems and increasing focus. This can be frustrating for parents who don't know where to start improving the diet for their child.
While the results for each child will vary, it is a common sense solution, and if effective is well worth the effort.
The Parenting Aspergers Resource Guide: A Complete Resource Guide For Parents Who Have Children Diagnosed With Aspergers Syndrome.