Starbucks drinks are customizable to the point that hundreds of flavor combinations are possible. So the chain’s “secret” menu isn’t really a secret; it’s limited to the drinker’s imagination.
Still, there are a number of popular “secret” Starbucks concoctions nestled around the blogosphere. Among the strangest is the Crunchberry Frappuccino, with a flavor profile inspired by (but not actually including) the cereal of the same name. It’s just the strawberry version of Starbucks' frozen blended drink with hazelnut syrup, and it’s purported to taste just like Crunchberries. Other popular “secret” Frappuccino flavors include cake batter (vanilla and almond flavoring added to a vanilla frap), raspberry cheesecake (raspberry syrup added to any white chocolate frap), and Nutella (chocolate, hazelnut, and caramel)