Your search for the softest hoodie stops here. Completely soft inside with no stinging seams or labels. With zipper to easy put on and off. If your child gets too warm quickly, a zipper is also the best option.
 
The hooded hoodie has subtle extras that help to reduce stress:
Loop in pocket for hooking on fidget material for subtle fidgeting.
Loop on cords for attaching subtle bite element. Bye bye bitten off cords and sleeves.
Biting and fidgeting has a stress-regulating effect and contributes to higher concentration.