I wonder what would happen if someone took a small tire, such as the
ones on wheelbarrows or push carts (dollys) and just filled them with
Spray Foam (such as "Great Stuff" brand).

It would seem to me, that you could just remove the valve stem core,
insert the nozzle from the spray can into the valve stem, and fill the
tire. I guess the only concern would be to make sure the whole tire was
filled, and not leaving parts of it empty. The foam would expand and
make a solid tire.

Has anyone ever tried this?