7-up cake, the fizzy cake! A creative experiment tried out by someone resulted in this light and airy cake. And the experiment was adding a few ounces of the soft drink 7-up instead of water to the batter. 7-Cup cake comes in three popular variants and all three beats the next when it comes to taste. The sheet cake, 3-layer torte, and the pound cake prepared in a Bundt pan are the three popular 7-Up cake varieties.