Preheat oven to 350ºF. Line 36 mini muffin tin holes with mini cupcake wrappers.
In a large mixing bowl, combine the brownie mix, water, applesauce, and egg whites. Mix 50 times with a wooden spoon (use 50 strokes); do not under or over mix. Pour the brownie mixture into prepared muffin tins, about 1 tbsp per hole.
While the cupcakes cool, to make the topping, stir together the whipped topping and peanut butter powder in a bowl. Divide the topping over the cooled cupcakes and sprinkle each with a few Fiber One bar pieces.