This delicious frosting is the perfect topper for our coca-cola layer cake, or any cake for a soda lover. Like a traditional chocolate frosting, it is made with butter, powdered sugar, cocoa powder, and vanilla, but we added coca-cola as well, to add a double dose of the sodas signature warm and spicy flavor. White sugar pearls give the top of the cake a fun and fizzy look, but they are completely optional.