Preheat oven to 350F degrees.
If you're using whole milk instead of buttermilk. In a small bowl, pour in the whole milk and 2 tsp vinegar (I used apple cider). Let stand for about 5 minutes until it starts to look curdled.
In a large mixing bowl or stand mixer, cream together the butter and sugar until light and fluffy. Add in the eggs, one at a time. Mix and then add the other. Add vanilla extract and mix until combined.
Next, add in the flour, sea salt, baking powder and baking soda and mix until well combined.
Slowly pour in the buttermilk or whole milk mixture and mix while adding it in until the dough is soft.
Fold in 1½ cups of sprinkles with a spatula very gently until just incorporated.
Divide batter between two spray & lined 9in cake pans.
Bake for about 45-55 minutes until a toothpick comes out clean! The edges will be lightly brown, and you want the top soft but set. Cover lightly with a piece of foil halfway through baking to make sure it doesn't get too brown.
Once done, cool on the baking sheet for about 5-10 minutes and then move to a wire rack to cool completely.