In a large mixing bowl, add the flour, sugar, baking powder, salt, and cinnamon and stir with a whisk to combine.
In a separate bowl, add the vanilla, milk, applesauce, and eggs and stir with a whisk to combine. Slowly whisk the dry ingredients into the wet to form the batter. Fold in the diced apples.
Heat a few inches of oil in a Dutch oven until hot (350F-370F) over medium-high heat. Test using a thermometer or drop a small amount of batter into the oil. If it bubbles and floats immediately, it's ready. If it burns quickly, the oil is too hot. Reduce the heat.
Drop one tablespoon of batter into the oil, six or seven at a time. Cook, flipping when needed, until the fritters are golden brown and cooked through, about 2-3 minutes. Remove with a slotted spoon to drain on a paper towel. Repeat.
For the glaze, in a small bowl, whisk together all the ingredients until smooth.
To serve, dust the fritters in powdered sugar or coat in the glaze.