There are several ways to soften brown sugar that has become too hard to scoop or measure for a recipe. If you need it quickly, you can use the microwave method. Place the brown sugar in a microwave-safe bowl and cover it with a damp paper towel. Microwave in intervals of 15 seconds, stirring in between until it softens. If you have a few hours or need your brown sugar the next day, place a piece of bread, a damp towel, or half an apple in the sugar's container and cover it. The moisture from these items will soften the brown sugar, usually within a few hours.