Adding fruit to a cake makes it seem more elegant, and there are many ways to incorporate it into a box cake mix. One way is to add a few spoonfuls of fruit preserves into the batter and swirl it around before baking. Chocolate cake will quickly turn into chocolate-raspberry cake. When making a layered cake, instead of spreading frosting in between each layer of cake, spread preserves in between each layer before frosting the top and sides of the cake. Or when using frosting in between each layer of cake, add a layer of fresh berries on top of each layer of frosting. The result is a fresh and delicious cake.