Step 1

Preheat oven to 350 degrees F (175 degrees C). Grease and flour a fluted tube pan (such as Bundt®).

Step 2

Beat cake mix, vegetable oil, club soda, eggs, and 1 package pistachio pudding mix together in a bowl until blended; pour into the prepared pan.

Step 3

Bake in the preheated oven until a toothpick inserted in the cake comes out clean, 30 to 40 minutes. Turn cake onto a cooling rack and cool completely.

Step 4

Beat milk, 1 package pistachio pudding mix, and whipped topping mix together in a bowl using an electric mixer on high until frosting forms stiff peaks. Spread frosting on cake.