Whisk together eggs, milk, salt, sugar, vanilla, and cinnamon in a flat-bottomed pie plate or baking dish. Split biscuits in half and place a few at a time into the egg mixture and flip to make sure both sides of biscuits are well-coated.
Melt butter in a large skillet or on a griddle. Place biscuit halves in skillet or on griddle and cook until golden brown on each side, about 3-4 minutes.
Serve immediately or keep warm in oven until ready to serve, but no longer than about 30 minutes.