Molasses

Molasses, mixed with turnips and potatoes, were once used by the Tenth Doctor to clog up proton cannons being fired upon him and Martha Jones. Having landed aboard an American schooner in the Caribbean Sea during the Quasi-War, the time travellers had to quickly prepare the mixture to thwart their attackers. The mixture gunked up the cannon's intake valve and immediately caused it to explode. (COMIC: Second Wave)