Have you ever gone to scoop some brown sugar just to find that it's super-lumpy or hard as a rock? You can keep that from happening with just a slice of bread.
You can also use a slice of bread to keep it from hardening up in the first place: Toss a slice of bread into your brown sugar container and close it up. The brown sugar will stay soft and the bread won't go mouldy.
Kitchen Tip: Keeping Your Brown Sugar Soft [This Week for Dinner]