1. Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
2. In a large mixing bowl, whisk together the all-purpose flour, sugar, baking powder, and salt until well combined.
3. Add the milk, vegetable oil, vanilla extract, and eggs to the dry ingredients. Mix until the batter is smooth and well incorporated.
4. Gradually add the warm water while mixing, continuing to blend until the batter is smooth.
5. Fill each cupcake liner about two-thirds full with the batter.
6. Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a cupcake comes out clean.
7. Remove the cupcakes from the oven and let them cool in the pan for a few minutes before transferring them to a wire rack to cool completely.

Buttercream Frosting:

1. In a large bowl, beat the unsalted butter at room temperature until light and fluffy using an electric mixer.
2. Gradually add the powdered sugar, one cup at a time, beating well after each addition.
3. Mix in the vanilla extract and a pinch of salt.
4. Add 2-3 tablespoons of water or milk to achieve your desired frosting consistency. Mix until the frosting is smooth and creamy.
5. Once the cupcakes are completely cooled, use a piping bag and a star-shaped tip to pipe the buttercream frosting onto the cupcakes.
6. Decorate with additional sprinkles or toppings, if desired.