Add the cake mix, unsweetened applesauce, water, eggs, and vanilla extract to a large bowl. Use a hand mixer on medium speed or mix vigorously by hand for 2 minutes until the cake batter is combined.
Lightly spray a 13x9-inch baking dish with coconut oil or canola oil. Then, pour the cake batter into the dish.
Bake the cake in the oven at 350°F for 28-33 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Wash and hull the strawberries. Then, cut all the strawberries into small pieces and add them to a large bowl with two teaspoons of sugar or your sweetener of choice. As an option, save a few strawberries to slice and decorate the top of the cake.
Thoroughly mash the strawberries with a potato masher to release the juices. Place the mashed strawberries in a strainer with a bowl underneath. Then, use a spoon to push down the strawberries to release the juices into a bowl. Repeat this process and squeeze as much strawberry juice out of the strawberries as you can, you should have about 1 cup of strawberry juice. Don’t discard the mashed strawberries, instead place them in another bowl and refrigerate them until you are ready to serve.
Once the cake is done, let it cool for 15-20 minutes. After that, poke holes about one inch apart all over the cake. The handle of a wooden spoon or a large straw is the perfect size.
Pour the reserved strawberry juice over the holes in the cake, ensuring it seeps into the holes. Then, cover the cake with foil and refrigerate it for 3-4 hours, or until ready to serve.
When ready to serve, add the reserved mashed strawberries on top of the cake. Then, spread the whipped topping evenly over the cake. As an option, garnish with additional sliced strawberries or add the mashed reserved strawberries on top of the whipped cream instead of putting them on the cake. Then, slice the cake, serve, and enjoy!