In a large, deep skillet, warm 2-3 inches of vegetable oil over medium heat to 375°F.
In a large bowl, whisk the flour, sugar, baking powder, cinnamon, and salt until well combined.
Make a well in the center, and add the milk, eggs, and vanilla. Whisk gently to break up the eggs, then stir into a thick batter. Fold in the diced apples.
Drop the batter in heaping tablespoon-sized portions into the hot oil. Work in small batches to keep from overcrowding the pan and dropping the oil temperature.
Cook the fritter bites, flipping as needed, until golden on all sides, about 1-2 minutes per side. Remove from the oil with a slotted spoon and drain on a paper towel-lined plate.
Whisk the powdered sugar and apple cider until smooth. Dunk the warm fritter bites in the glaze, turning with a fork to coat fully.
Place on a wire rack to drip and dry. Serve warm or at room temperature, and enjoy!