Preheat the oven to 425°F.
In a small bowl, whisk together the mashed sweet potatoes, apple cider vinegar, and milk. Set aside.
Add the flour, baking powder, salt, and cold butter to a food processor. Pulse until the butter is fully broken up and the mixture resembles a coarse, crumbly texture.
Add the sweet potato mixture to the food processor and blend just until fully combined. The dough will be wet and sticky.
Generously flour a clean work surface. Using a silicone spatula, transfer the dough onto the floured surface.
Lightly flour the top of the dough and gently flatten it into a circle about 1/2-inch thick.
Use a large biscuit or cookie cutter to cut out 12 biscuits.
Transfer biscuits to a baking sheet lined with parchment paper or a silicone baking mat.
Bake for 15 minutes, or until the tops are lightly golden.
Let cool slightly, then slice in half and enjoy warm.