In a bowl, whisk together the cake mix, club soda and vanilla until well blended.
Scrape batter into the prepared baking pan.
Place in the center of the oven and bake until a thin knife inserted into the center comes out clean, about 25 to 35 minutes.
Remove from the oven and place on a wire rack to cool.
When cool, remove from the pan and spread with a very thin coating of your favorite frosting.
Notes
Serving size: 1 slice (1/8th recipe)WW Points: 9Check the WW Points for this recipe and track it in the WW app. (Must be logged into WW on a smartphone or tablet.)4PointsPlus (Old plan)Using a full-size cake mix? Adjust the club soda to match the weight of your cake mix: use 1? cups for a 13.25-ounce box, about 1¼ cups for a 14.25-ounce box, or about 1? cups for a 15.25-ounce box. The original 18.25-ounce boxes used about 1½ cups (12 ounces). These amounts are based on the proportions in my original small-cake recipe and may need slight adjustment depending on the cake mix.Cake and Soda Combinations:
Carrot cake mix + diet ginger ale
Chocolate cake mix + diet cola
Chocolate cake mix + diet root beer
Lemon cake + lemon-lime sparkling water or soda
Spice cake + ginger ale or ginger beer
Strawberry cake mix + berry flavored sparkling water or soda