Purchase 1 yard of jersey fabric with two-way stretch. This is the same material used to make T-shirts. You will fold the fabric in half, so the tunnel will be 1/2 a yard wide. If you're child is older or larger, purchase more fabric as needed.
Fold the fabric in half, right sides together, width wise. If your fabric is one yard long and 60 inches wide, your tunnel will be 60 inches long and 1/2 a yard wide. Pin along the long edge of the fabric to form a tube.
Sew along the pinned edge of the fabric. Turn the fabric tube right-side out. Your child can enter one end of this sensory tube and crawl through to the other. The short length of the tunnel allows your child to see the light at the other end, which may help him overcome any fear he feels with regard to this activity.