For the cupcakes: Preheat the oven to 350 degrees F. In a measuring cup, mix together the milk and vinegar to make sour milk. In a large bowl, add the cocoa powder and hot water and mix together with an electric hand mixer. Add the soured milk, granulated sugar, shortening, vanilla extract and eggs, and mix together. Next, add the flour and baking soda and mix until all the ingredients are incorporated.
Place cupcake liners into a cupcake pan and fill each halfway with batter. Bake until a toothpick inserted into the center comes out clean, 15 to 18 minutes. Cool in the pan for 5 to 10 minutes.
For the frosting: Whip 4 cups of the confectioners' sugar, the butter and vanilla extract with an electric hand mixer until smooth, while slowly adding the milk.
Add food coloring to achieve desired color and the remaining 4 cups confectioners' sugar.
Frost the cupcakes and top with sprinkles.