Once cereal has lost its crunch, it loses its appeal. Instead of tossing it in the trash, make it fresh and crispy again. Cereals usually have a fairly long shelf life and will last in your pantry for weeks when properly stored. But if you leave the cereal box open instead of putting it in an airtight container, it may become stale due to exposure to moisture in the air. Stale cereal that still has its original flavor can be used for baked goods or snack mixes or you can recrisp the stale cereal and continue to eat it for breakfast.
Preheat your oven to 425 degrees Fahrenheit. Pour the stale cereal onto a large cookie sheet. Spread the cereal out in a single layer.
Place the cookie sheet in the oven for 3 to 4 minutes. Remove the cookie sheet from the oven using oven mitts.
Allow the cereal to cool completely on the cookie sheet. It must come to room temperature or it will quickly become stale again.
Pour the cereal into an airtight container. Seal the lid tightly and store in your pantry.