Doom-Foam is a liquid substance designed to harden in seconds, trapping whoever is caught in it. Developed by Doctor Robotnik, it was used by Commander Brutus to capture Sonic the Hedgehog. However, since the hedgehog was currently Super Sonic, he easily broke out of his mobile prison. After this, the Foam Cannon was deemed to be pointless.
The chemical seems to be a precursor to Mega-Glue, another material designed to quickly harden and trap its prey. However, there is no known antidode for Doom-Foam (other than a hammer and chisel).