The action of ketchup, hot sauce, barbecue sauce, etc. on copper coins is due to the vinegar and salt. I don't think I would try this on any high-ticket coins, but for run-of-the-mill coins, give it a try. Dissolve the salt in the vinegar and use it to dip/soak the coins. Remember to rinse the Be-Jesus out of them, any residue is deadly for the coins.