Baking trays pose a slight cleaning challenge, because they are too large to fully fit in most kitchen sinks to soak and are often in need of soaking--baked goods get stuck to the tray's surface during cooking and leave remnants that are difficult to remove quickly. Some cleaning methods make the process easier, however, no matter if the tray is metal or glass.
Place the baking tray in your kitchen sink after allowing it to cool. You may need to lay it at an angle, if your sink is too small to accommodate the tray. Rest the tray against a towel, if you are concerned about scratches to the tray bottom or the sink.
Pour dish detergent directly on the tray, covering the entire top (food-side) surface. Allow the detergent to sit on the surface undisturbed for up to 30 minutes, then dampen a sponge in hot water and start scrubbing the tray.
Scrub the edges of the tray and around the rim where cooking oil and other substances often collect. Use a soft-bristled toothbrush or bottle brush.
Rinse the tray with hot water from the faucet. If any food remains stuck to the tray, pour more dish detergent on the areas and scrub with the sponge.
Turn the tray over and place a few drops of detergent on the bottom. Scrub this with a sponge and rinse. Dry the tray with a towel, or place it in your dish drainer.
If a lot of the surface contains stuck-on food, and the tray is too large to lay down in your sink, alternatively leave the tray soaking in a bathtub overnight. Just fill it enough to cover the tray and add dish soap to the water.
If your baking tray is aluminium, the GE Appliances website advises you can use a soap-filled steel wool scrubber to clean these. You may also use these scrubbers on uncoated glassware. However, do not use steel wool on any stainless-steel baking tray or any containing a non-stick coating--the steel wool can damage these surfaces. In most cases, the least abrasive cleaners and cleaning tools are safest at preventing permanent damage to your bakeware.