Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Combine cake mix and soda in a large bowl. Use a hand whisk to mix ingredients until light and smooth, about 3 minutes. Pour batter into a prepared baking dish.
Bake cake in the preheated oven until a toothpick inserted in the center comes out clean, 35 to 40 minutes. Allow cake to cool before cutting.
