Brandi Long
The directions do not state what to do with the vinegar. I assume it's to mix with the milk, as I've used a milk/vinegar mixture to substitute for buttermilk. 
From my experience, you mix the vinegar with milk and let sit for 15 minutes before adding it to recipe. 
However, I made this without the vinegar and they turned out great! I added vanilla extract and cinnamon, as well.