Simple Buttermilk Substitutions - I read another pin saying: Place Tablespoon white vinegar or lemon juice in a liquid measuring cup. Add enough regular milk to bring the liquid up to the cup line. Let stand for 5 minutes, then use in the recipe.
Baking Substitutions — There are a variety of reasons you might need to find a substitute for one of the ingredients in a recipe: availability, allergies and other dietary restrictions, or you just might not care for something.
Buttermilk Substitutes: Place a Tablespoon of white vinegar or lemon juice in a liquid measuring cup. Add enough milk to bring the liquid up to the one-cup line. Let stand for five minute. Then, use as much as your recipe calls for.