Sometimes I am the queen of preparation. Sometimes I am not.
For the times when you are not and you completely space the buttermilk that is included in the recipe for the baked donuts that you wanted to try, for like 3 months, fear not! There is a way. There is a substitution (and I learned it from the brilliant Pioneer Woman, obviously).
It is called milk and vinegar! Sounds gross, I know. But it works.
Since buttermilk is essentially just sour milk, when you add vinegar to regular milk, it does the curdling/souring process for you. All you do is pour regular milk to just under your desired amount of buttermilk. Then, top it off with white vinegar, let it sit for a few minutes and presto! You have buttermilk.
Milk + Vinegar = The easiest buttermilk substitution ever!
P.S. I found a couple of other buttermilk substitutions, but they call for yogurt or lemons, healthy ingredients that I never have around the house. If you try them, let me know how they work!