Milk and vinegar

Adding vinegar to milk gives it an acidity similar to that of buttermilk. You may use distilled white vinegar or other types of vinegar, although the latter has a more neutral flavor. Any type of milk can be used, but if your recipe asks for a specific type of buttermilk, such as low-fat, it could be advisable to substitute with milk of a similar type.

The easiest substitute for buttermilk is 1 Tbs. of vinegar mixed with 1 cup of milk. After giving the mixture a gentle stir, wait for about five minutes. Lemon juice and cream of tartar are other excellent substitutes for buttermilk if you don't have vinegar. Even though many sources advise waiting 5–10 minutes before using the mixture in your recipe, experts say it's not required.