How to Make It
In a large bowl, combine dry cake mix, 1-1/4 cups root beer, oil and eggs; beat until well blended. Pour into a greased 13"x9" baking pan.
Bake at 350 degrees for 30 to 35 minutes; cool completely.
In a medium bowl, with an electric mixer on high speed, beat whipped topping mix and remaining root beer until soft peaks form; frost cake.
101 Easy Everyday Recipes Cookbook