Not-So-Perfect Birthday Sheet Cake

Featured in: Sweet & Simple

This playful birthday sheet cake is moist, tender, and topped with charming swirls of colorful frosting and rainbow sprinkles. All-purpose flour and sour cream create a soft crumb, while real butter brings richness. Simple pantry ingredients are mixed to produce a batter that's baked in a classic 9x13-inch pan for easy serving. After baking, whip up a creamy vanilla butter frosting and swirl generously over the cooled cake, embracing imperfection for a joyful finish. Bright sprinkles add a festive touch, making this treat perfect for birthdays, holidays, or any happy occasion. Slice directly in the pan and serve for a celebration that's delightfully homemade.

Updated on Thu, 30 Oct 2025 14:31:00 GMT
Colorful Not-So-Perfect Birthday Sheet Cake topped with whimsical sprinkles and tasty frosting.  Save
Colorful Not-So-Perfect Birthday Sheet Cake topped with whimsical sprinkles and tasty frosting. | munchhug.com

A playful, moist, and colorful sheet cake designed to celebrate any occasion—deliciously homemade with charmingly imperfect swirls of frosting and sprinkles.

Our family is big on sheet cakes for birthdays and gatherings. The cheerful frosting swirls and generous sprinkles always spark laughter—no perfection needed! It is my favorite way to make everyone feel special with minimal fuss.

Ingredients

  • All-purpose flour: 2 1/2 cups (325 g)
  • Granulated sugar: 2 cups (400 g)
  • Baking powder: 1 tablespoon
  • Salt: 1/2 teaspoon
  • Whole milk, room temperature: 1 cup (240 ml)
  • Unsalted butter, melted and slightly cooled: 3/4 cup (170 g)
  • Large eggs, room temperature: 4
  • Vanilla extract: 2 teaspoons
  • Sour cream, room temperature: 1/2 cup (120 ml)
  • Unsalted butter, softened: 1 cup (225 g)
  • Powdered sugar, sifted: 4 cups (480 g)
  • Whole milk (for frosting), more as needed: 1/4 cup (60 ml)
  • Vanilla extract (for frosting): 2 teaspoons
  • Pinch of salt (for frosting)
  • Food coloring: assorted colors, optional
  • Rainbow sprinkles: 1/3 cup (60 g)

Instructions

Prepare the pan:
Preheat oven to 350°F (175°C). Grease and line a 9x13-inch (23x33 cm) sheet pan with parchment paper.
Mix dry ingredients:
In a large bowl, whisk together flour, sugar, baking powder, and salt.
Combine wet ingredients:
In a separate bowl, whisk milk, melted butter, eggs, vanilla, and sour cream until smooth.
Combine batter:
Pour wet ingredients into dry ingredients and stir until just combined. Do not overmix.
Transfer & bake:
Transfer batter to prepared pan. Smooth the top with a spatula. Bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out clean.
Cool:
Cool cake completely in the pan on a wire rack.
Make frosting:
Beat butter until creamy. Gradually add powdered sugar, mixing well. Add milk, vanilla, and salt. Beat until fluffy. If desired, divide frosting into bowls and tint with food coloring.
Decorate:
Dollop or swirl frosting onto cooled cake using a spatula. Embrace imperfect swirls and texture.
Add sprinkles & serve:
Scatter generously with rainbow sprinkles. Slice and serve directly from the pan.
Save
| munchhug.com

Making this sheet cake has become a birthday ritual—kids love choosing their frosting colors and scattering sprinkles by the handful. The first slice is always the best, especially eaten straight from the pan with a spoon.

Required Tools

9x13-inch (23x33 cm) sheet pan, mixing bowls, whisk, spatula, electric mixer (optional), parchment paper

Allergen Information

Contains wheat (gluten), eggs, milk, and dairy (butter, sour cream). Check sprinkle packaging for potential nut or gluten contamination.

Nutritional Information

Calories: 410, Total Fat: 18 g, Carbohydrates: 59 g, Protein: 4 g

Vibrant Not-So-Perfect Birthday Sheet Cake bursting with flavor and cheerful frosting swirls.  Save
Vibrant Not-So-Perfect Birthday Sheet Cake bursting with flavor and cheerful frosting swirls. | munchhug.com

Even if your swirls aren&t perfect, the cake will taste amazing—enjoy sharing every slice and celebrating in style.

Recipe Guide

What makes this cake moist and tender?

Sour cream, eggs, and melted butter in the batter create a soft, moist texture with a rich crumb.

Can I customize the frosting colors?

Yes! Add food coloring to divided frosting batches for colorful swirls, or keep it classic with plain vanilla frosting.

How should I store leftovers?

Cover and store at room temperature for up to 2 days, or refrigerate for up to 5 days for extra freshness.

Is there a chocolate version?

For chocolate flavor, swap 1/2 cup flour with cocoa powder when mixing dry ingredients.

Which pan size is best for this cake?

A 9x13-inch sheet pan is ideal for baking and serving straight from the pan.

Are there allergen considerations?

Contains wheat, eggs, milk, and dairy. Check sprinkle packaging for possible nut or gluten traces.

Not-So-Perfect Birthday Sheet Cake

Tender homemade sheet cake with imperfect swirls of frosting and sprinkles, perfect for any celebration and easy to make.

Prep duration
25 min
Heat time
30 min
Complete duration
55 min
Created by Samantha Reed


Skill level Easy

Heritage American

Output 12 Portions

Nutrition preferences Meat-free

Components

For the Cake

01 2 1/2 cups all-purpose flour
02 2 cups granulated sugar
03 1 tablespoon baking powder
04 1/2 teaspoon salt
05 1 cup whole milk, at room temperature
06 3/4 cup unsalted butter, melted and cooled
07 4 large eggs, at room temperature
08 2 teaspoons vanilla extract
09 1/2 cup sour cream, at room temperature

For the Frosting

01 1 cup unsalted butter, softened
02 4 cups powdered sugar, sifted
03 1/4 cup whole milk, plus more as needed
04 2 teaspoons vanilla extract
05 Pinch of salt
06 Food coloring (assorted colors, optional)

For Decorating

01 1/3 cup rainbow sprinkles

Method

Phase 01

Prepare Baking Pan: Preheat oven to 350°F. Grease and line a 9x13-inch sheet pan with parchment paper.

Phase 02

Mix Dry Ingredients: Combine flour, sugar, baking powder, and salt in a large mixing bowl. Whisk thoroughly.

Phase 03

Mix Wet Ingredients: In a separate bowl, whisk together milk, melted butter, eggs, vanilla extract, and sour cream until the mixture is smooth.

Phase 04

Combine Batters: Add the wet mixture to the dry ingredients. Stir just until incorporated. Do not overmix.

Phase 05

Transfer Batter: Scrape batter into the prepared pan and smooth the top using a spatula.

Phase 06

Bake: Bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out clean.

Phase 07

Cool Cake: Allow the cake to cool completely in the pan on a wire rack.

Phase 08

Make Frosting: Beat softened butter with an electric mixer until creamy. Gradually blend in powdered sugar, then add milk, vanilla extract, and salt. Beat until light and fluffy. For colored frosting, divide into bowls and tint with food coloring as desired.

Phase 09

Frost Cake: Swirl or dollop the frosting onto the cooled cake with a spatula, embracing textured and imperfect swirls.

Phase 10

Decorate: Scatter rainbow sprinkles generously over the frosted cake.

Phase 11

Serve: Slice and serve directly from the pan.

Tools needed

  • 9x13-inch sheet pan
  • Mixing bowls
  • Whisk
  • Spatula
  • Electric mixer
  • Parchment paper

Allergy alerts

Review ingredients carefully for potential allergens and seek professional medical guidance if concerned.
  • Contains wheat (gluten), eggs, milk, and dairy products.
  • Check sprinkle packaging for potential traces of nuts or gluten.

Dietary info (per portion)

Values shown are estimates only - please consult healthcare providers for specific advice.
  • Energy: 410
  • Lipids: 18 g
  • Carbohydrates: 59 g
  • Proteins: 4 g