Preheat oven to 400° F. Line a baking sheet with parchment paper and set aside.
Combine the milk and vinegar. Gently stir and set aside. This will allow the milk to slightly curdle, giving it a buttermilk-like texture and taste.
In a medium bowl, whisk together the flour, sugar, baking powder, and salt.
Add the cold cubed butter to the flour mixture. Using a pastry cutter, or your fingers, cut the butter into the flour until it resembles pea-sized crumbs.
Add in the milk/vinegar mixture, or buttermilk, and stir until the mixture just comes together. Do not overmix.
Turn the dough out onto a floured suface. Gently work the dough with your hands until it comes together into a cohesive mass. If the dough is too sticky, add flour until it is manageable.
Still using your hands, flatten the dough out into a rectangle, about 1-inch thick. Fold the dough onto itself, then flatten it out again and fold again. Repeat about 10 times. This creates the layers of the biscuits.
Form the dough into a 1-inch thick rectangle again. Cut the rectangle in half length wise, then cut each half in thirds, to create 6 even-sized biscuits.
Transfer biscuits to prepared baking sheet. Brush the top of each biscuit with additional milk or buttermilk, then sprinkle everything bagel seasoning on top.
Bake for for 17-18 minutes, or until golden brown. Serve warm.