Children with autism frequently have sensory sensitivities and motor function difficulties that may make some craft projects hard for them to do. Both of these things need to be taken into account when deciding on project for them. Doing craft projects with kids with autism may have a therapeutic effect and will teach them better motor control while giving them sensory stimulation.
Many kids with autism love visual input and can spend hours staring at something they find fascinating. Find fabrics with different colors, textures and patterns and cut them into random strips or shape. Help the child to mount the fabric to a piece of plain cloth (preferably white or another non distracting color) using a glue gun. If the child is dexterous enough you may be able to let them glue or sew it on themselves.
You can use this process to make a wall hanging, or if you sew it and finish the edges appropriately, you may even use it as a pillow or blanket.
Many autistic children are sensitive to the way things feel, which may prompt an extreme reaction in some. Help the child learn to manage their sensitivity and widen the parameters of what is acceptable to their tactile senses with fun crafting projects.
You can use clay to make all of the typical childhood projects like snakes and bowls as well as more complex work. The major thing to be aware of is that the motor function of children with autism may be varied or uneven. Provide a number of different clays with different textures ranging from soft and hard to wet, sticky and gooey. Start with the textures the child is most comfortable with and slowly introduce the other clays.
Many kids with autism will eat only a limited variety of foods. Bringing them into the kitchen may make them more willing to experiment with flavors, textures and colors.
Use a few basic recipes such as sugar cookies, plane cheesecake, sandwiches, or a family meal staple. Offer the child a variety of different seasonings, vegetables, fruit, food dyes and flavorings to that they can make their own concoctions. Let them put whatever edible thing they want in a small, portion sized pot so that they can taste it. Keep in mind that some children with autism are sensitive to food coloring so you may want to replace them with bright flowers or plants like roses that bleed color.