You can make your own buttermilk easily at home with just regular milk and vinegar! 1. Add 2 1/2 teaspoons of white vinegar into a liquid measuring cup and then using milk, fill it up to the 2/3 cup line. 2. Stir it to combine and then let the buttermilk sit for 5 minutes. It should thicken up and curdle the milk slightly creating your own buttermilk!