Soften brown sugar quickly by placing it in a bowl covered with a damp paper towel. Microwave it for 20 seconds at a time until it becomes soft. Another option is to place pieces of brown sugar in a food processor, and pulse or chop until the sugar reaches the desired consistency.
Another way to soften brown sugar quickly is to place the sugar in a baking pan and place the pan in a 250-degree Fahrenheit oven for five minutes. If the brown sugar is still too hard, leave the pan in the oven, and check it every few minutes until the brown sugar is ready for use.
If the brown sugar is not needed immediately, place it in an airtight container along with several apple slices, and remove the apple slices after a day or two when the brown sugar has softened. If apple slices are not available, substitute a slice of fresh bread instead.
Placing the brown sugar in a bowl covered with a damp cloth and allowing it to sit overnight is another method of softening it. Sprinkling a few drops of water on hardened brown sugar, placing it in a plastic bag and allowing it to sit for a few days also works.