A non-stick baking tray is designed to be easy to clean. This isn't always the case, however, when it comes to burnt-on grease. Grease stains on your baking tray can create a dirty, dingy look even after you've washed the sheet with soap and water. Luckily, most grease stains will come off of a non-stick baking tray if you treat them with the proper techniques and tools.
Fill your sink or a basin with white vinegar and completely immerse the baking tray in the vinegar.
Allow the baking tray to soak for one to two hours.
Lift the baking tray out of the vinegar, but do not dry it off. Instead, sprinkle baking soda over the sheet.
Scrub the sheet gently with a scrubbing sponge. The baking soda and vinegar will create a gentle scouring paste. This should remove any left over residue.
Rinse the baking tray thoroughly and dry it with a cloth or dish towel.