Preheat oven to 375 and spray a 10"x15"x1" baking pan with non-stick cooking spray, set aside,
In a bowl of a stand mixer add your flour, sugar, salt, baking soda and baking powder.
Whisk until this is combined, set aside.
In a small saucepan, add your butter water.
Heat over medium heat until butter is melted.
Add this mixture to your flour mixture and beat until combined.
Add in your eggs, vanilla extract and sour cream and beat until combined.
Next add in your rainbow sprinkles.
Fold in sprinkles until they are evenly distributed among your batter.
Pour into baking pan and bake. for 18-22 minutes, remove and cool completely