Heat oven to 350°F.
Spray bottom of 9x13 pan with non-stick cooking spray.
In large bowl, beat cake mix, water, oil and egg whites with electric mixer until combined. Pour cake mixture into baking pan and cook for length on package (probably about 25-30 minutes) or until toothpick inserted in center comes out clean.
Remove cake from oven and let cool in baking dish.
Boil 1 cup of water and mix gelatin package in water until dissolved. Add ½ cup cold water.
Using tongs of a fork, poke holes in cake, about every ½ inch.
Pour dissolved strawberry gelatin over top of cake. Let cool completely, about 1 hour.
Spread whipped topping over top of cake. Garnish slices with fresh strawberries.