Heat the oven to 350°F (175°C). Grease a 10- to 12-cup Bundt pan very well with baking spray.
Add the red velvet cake mix, pudding mix, eggs, sour cream, and water to a large bowl.
Beat until smooth and evenly combined.
Pour the batter into the prepared Bundt pan.
Bake for 35 to 40 minutes, until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Let the cake cool in the pan for 30 minutes. Invert onto a wire rack or serving plate and cool completely.
For the frosting, beat the cream cheese and butter until smooth.
Gradually add powdered sugar, mixing after each addition. Add vanilla and beat until creamy.
Warm the frosting in a microwave-safe bowl in 5-second intervals until it becomes thick but pourable.
Pour frosting over the cooled cake. Decorate with berries and optional sprinkles.