Ever had a recipe call for buttermilk? Not something we typically keep in the house. Though if you do happen to buy some, you can freeze it in ice cube trays. Once frozen, pop them out and put in a container or freezer bag.
But here's how you can make buttermilk in a pinch -
Put 1 tablespoon white vinegar or lemon juice in a measuring cup.
Fill to 1 cup mark with milk.
Let stand 5 minutes.