Before you replace those old cookie sheets, try filling the sink with a solution of hot water, 1/2 cup baking soda, and 1/2 cup white vinegar. Soak your pans for at least 30 minutes. Now scrub with steel wool or a non-abrasive scrubber for non-stick pans. Rinse and dry. The baking soda and vinegar created a bubbly mix that loosened any gunk while the acetic vinegar dissolved any residue.