I have used many different pieces of fruit; apple, orange, lemon, even a slice of bread to sit in the big container of brown sugar. I have also had the unpleasant surprise of finding that the moist item has gone moldy. So sometimes I use this method. I dampen a rolled up piece of paper towel, put it into a condiment cup to prevent it from wicking the colour out of the sugar, and seal it into the container with the sugar. It works.