Preheat your oven to 350°F (180°C) and spray your large loaf pan with non-stick cooking spray.
In a large bowl, add in the softened butter and sugar, then mix with a hand mixer until light and fluffy.
Add in the eggs and vanilla extract, and mix till they're combined. Now, add in the sour cream and milk, and mix until everything is well combined. Set aside.
In another bowl, add in all the dry ingredients; flour, baking powder, baking soda, salt, and cinnamon, and whisk together.
Add the dry ingredients to the wet ingredients, and stir until they're combined with no dry ingredients showing.
Add in the sprinkles, and mix gently for a couple of seconds.
Pour the batter into the loaf pan, and bake in the preheated oven for about 65-75 minutes (or until a toothpick comes out clean through the center and the top is golden).
Now, remove from the oven and allow to cool for 5 minutes in the pan, then transfer to a wire rack to keep on cooling.
To make the glaze, whisk together the sugar, heavy cream, and vanilla. Now, you can spread it over the cooled bread using a spatula.
Sprinkle some extra Christmas sprinkles on the glaze to enhance the appearance.
Viola! Your delightful Christmas bread is ready, and it's time to serve.