Unplug the toaster oven. Soak a cleaning cloth in warm water and wipe down the toaster oven. Put a couple of drops of dish-washing liquid onto the cloth and clean as much of the debris off as you can.
Rinse the cloth. Make a paste with the baking soda and water and smear the paste over the scorch marks. Leave it on for a few minutes and wipe off.
Pour some white vinegar onto the cloth and wipe down the oven. The acidity of the white vinegar will help to remove the scorch marks. Wipe the vinegar off with a clean cloth. Clean the surface thoroughly and leave to dry.