Skip the box mix – this homemade Funfetti Sheet Cake is soft, buttery, and packed full of sprinkles. Topped with fluffy vanilla buttercream, it’s a guaranteed crowd-pleaser for birthdays, celebrations, or any sprinkle-worthy day. Homemade funfetti – even better than you remember it!

There’s something about Funfetti cake that instantly brings back memories of childhood birthday parties, and rainbow sprinkles. But this version ditches the mix and keeps everything you do want: soft, moist vanilla cake with real butter flavor and that signature burst of color from sprinkles in every bite.

It’s no surprise around here that I love funfetti, as we’ve covered everything from funfetti cheesecake to funfetti babka, and of course a funfetti layer cake and funfetti bundt cake, so it was certainly time to add a funfetti sheet cake to the recipe archives. And since June is both my birthday month AND Bunsen Burner Bakery’s anniversary (fourteen years!), funfetti seemed like the perfect recipe for June’s “Sheet Cake of the Month.”

I’ve tested this recipe more times than I care to admit (all in the name of research, of course), working toward the perfect balance of tender cake texture and rich flavor. Sheet cakes are also incredibly easy to serve—no stacking layers or fancy decorations needed. Just bake, frost, and slice.

We’re using milk for moisture, sour cream for a soft crumb, and both butter and oil to get that rich flavor and keep the cake tender for days. The vanilla buttercream on top is whipped until light and airy and finished with, of course, more sprinkles.

If you’ve ever been disappointed by a dry or overly sweet Funfetti cake, this one will change your mind. It’s light without being too fluffy, sweet but not cloying, and has enough sprinkles to make every bite feel festive. And yes, I tested it with different sprinkle types (more on that below!).

Ingredients and Substitutions

• Butter: The butter should be cool room temperature, approximately 65°F.
• Granulated Sugar
• Eggs: Use room temperature eggs for the best incorporation. The texture will be a little different, but flax eggs can work to keep the cake egg-free.
• Oil: Use a neutral oil, like vegetable oil or avocado oil, to keep the cake extra moist.
• Sour Cream: Use full-fat sour cream at room temperature.
• Vanilla Extract: Don’t skip – this provides lots of flavor!
• Almond Extract: Adding almond extract adds the extra cake batter flavor to the cake, but can be omitted for nut allergies or preferences.
• All-Purpose Flour: Use a gluten-free flour mix containing xanthan gum for a gluten-free funfetti cake.
• Cornstarch: Using cake flour provides a lighter, softer crumb, but since not everyone keeps cake flour around, we’re going to make our own by adding cornstarch to the all-purpose flour.
• Baking Powder
• Baking Soda
• Salt
• Milk: Use whole milk for the best flavor and texture, or a non-dairy milk with high protein content, such as pea protein milk or soy milk.
• Rainbow Sprinkles: The long, soft kind. Avoid nonpareils, as they bleed into the batter.
• Confectioners’ Sugar
• Heavy Cream

How to Make Funfetti Sheet Cake

1. Cream the Butter: Using an electric mixer, cream the butter and sugar until light and fluffy. Add the eggs, followed by the vanilla and almond extracts. Add the vegetable oil and sour cream, mixing until fully combined.

2. Mix Dry Ingredients: Whisk the flour, cornstarch, baking powder, baking soda, and salt in a separate bowl.
3. Alternate Wet and Dry Ingredients: Add half the dry ingredients to the batter and mix to combine. Add the milk, mix well, and add the rest of the dry ingredients, mixing just until no dry patches of flour remain.

4. Add the Sprinkles: Gently fold the sprinkles into the batter – don’t overmix to avoid color bleeding.

5. Bake the Cake: Transfer the batter to a 9×13-inch cake pan and bake until golden and set. Cool the cake completely.

6. Make the Buttercream: Beat the butter until fluffy, then add powdered sugar, vanilla, and heavy cream. Fold in the sprinkles.

7. Frost and Decorate: Spread the frosting evenly over the cake and top with even more sprinkles.

Best Sprinkles for Baking

Not all sprinkles behave the same in cake batter. If you’ve ever baked a Funfetti cake and ended up with streaky batter or all the sprinkles at the bottom, you’re not alone!

The type of sprinkle you use can make or break your funfetti cake. Nonpareils – the tiny round balls – tend to bleed quickly when mixed into wet batter. They’re best for decoration only. Custom-dyed sprinkles also bleed. Your best bet are store-bought rainbow sprinkles, which are coated with a thin layer of wax which helps them stay intact in the oven and keeps the color from bleeding.

Kitchen Chemistry

Jimmy-style rainbow sprinkles are the best for baking because the waxy coating slows the release of the color into liquid batter and helps preserve distinct bursts of color in a cake.

To prevent the sprinkles from sinking to the bottom, the cake batter is thick enough to support them, and we won’t fold them in (gently!) until the last step. And while rainbow sprinkles are classic for a funfetti cake, swapping out the sprinkles is the perfect way to match a party theme or a holiday!

Tips and Tricks for the Best Funfetti Sheet Cake

1. Use Room Temperature Ingredients: Using butter, sour cream, eggs, and milk at room temperature helps the batter mix evenly for a better crumb.
2. Add Cornstarch: Adding cornstarch to the flour reduces the gluten percentage of the cake, creating a softer, more tender crumb.
3. Cool Completely Before Frosting: If the cake is even a little bit warm, the frosting will me.t
4. Double Up: To serve even more people, double the recipe – make two layers of cake and stack them on top of each other. Double the frosting recipe as well.
5. Half-Sheet Pan: To bake this cake in a 13×18-inch half-sheet pan for a larger cake, use 1.5x all ingredients for a 1-inch high pan (a standard half-sheet pan); if you have a tall-sided half-sheet pan, you can double the ingredients.
6. Make it Ahead: This cake stays moist for days and tastes even better after sitting overnight.
7. Storage: The cake will last for 4 days at room temperature. For long-term storage, wrap individual slices in plastic wrap and store in an airtight container in the freezer for up to 3 months. Defrost the cake at room temperature for a quick treat.
8. Recommended Tools: 9×13-inch Metal Baking Pan | Stand Mixer | Offset Spatula | Mixing Bowls | Rainbow Sprinkles