There are different grants for different things. I don't know of any grant that will help with basic necessaries but there are grants for things like assistiive technology, therapies,home modifications or vehicle modifications. Each state should have Medicaid waivers that people with various disabilities can be eligible for to get in home services that allow the parent or caregiver an opportunity to work. I don't know what state you are in but you may want to start by contacting your local disability office or center for independent living.

I have heard of Autism Speaks giving funding to a single parent with a child on the spectrum, however I do not know the steps to access that.