Preheat your oven to 350°F. Grease and flour a 9×13 inch baking pan.
In a large bowl, combine the cake mix, water, oil, and eggs. Beat on medium speed for 2 minutes until smooth.
Pour the batter into the prepared pan, spreading it evenly. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
While the cake bakes, prepare the berry syrup. In a medium saucepan, combine the berries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the berries release their juices and the sugar dissolves, about 10 minutes. Remove from heat and strain to remove seeds, pressing the mixture through a sieve.
Once the cake is done, let it cool for 10 minutes. Then, using the handle of a wooden spoon, poke holes all over the cake, about 1 inch apart.
Pour the warm berry syrup over the cake, allowing it to seep into the holes. Let the cake cool completely.
For the topping, whisk together the instant pudding mix and cold milk for 2 minutes until thick. Spread the pudding over the cooled cake.
In a separate bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form. Spread this whipped cream over the pudding layer.
Refrigerate the cake for at least 2 hours before serving, allowing the flavors to meld beautifully.
