In a small bowl, mix the plant-based milk with the apple cider vinegar and set aside. It will thicken after a few minutes; essentially becoming a vegan "buttermilk".
In a medium bowl, mix the flour, baking powder, and salt. Set aside.
In a large bowl, mix the vegan butter and 1 cup sugar with a wooden spoon about 2 minutes until well-combined and fluffy.
Add the vanilla extract and milk/vinegar mixture to the butter/sugar mixture and mix to combine.
Add the flour mixture 1/3 at a time, mixing after each addition and stirring until just incorporated.
Place the dough in the fridge and allow it to chill and firm up for 30 minutes - 1 hour.
Meanwhile, preheat the oven to 375 degrees F and line 2 baking sheets with parchment paper. Combine 3 tablespoons sugar with the cinnamon in a small bowl.
Use a tablespoon measure to scoop out the dough and roll it into balls (about 1-inch); I ended up with 27. Roll the dough balls in the cinnamon-sugar mixture.
Place the balls 2 inches apart on the baking sheets. Bake one sheet at a time in the center of the oven for 8-9 minutes.
Remove from oven and let cool slightly before serving. Let cool completely before storing in an airtight container; about 3 days at room temperature or a week in the fridge.
*I used Zulka Morena Pure Cane Sugar, which is unrefined, non-GMO, and vegan-friendly. Many white sugars are filtered through charred animal bones (known as bone char) to make the sugar white, and are thus not vegan. Look for organic or "no bone char" sugar.
**You can use all regular (Cassia) cinnamon OR a combination of regular and Ceylon cinnamon, aka Mexican cinnamon.