Beat sugar and eggs on medium speed for 1-2 minutes in a large bowl.
Add flour, baking powder, cinnamon, salt, and milk to the egg mixture, then mix until just combined.
In a separate bowl, mix the apple cubes with lemon juice, then add this mixture to the batter and stir with a spoon (do not use the mixer) until combined.
Pour fat into a high-sided saucepan and heat to 175-180°C (347-356°F). Alternatively, use a deep fryer set to this temperature.
Once the fat reaches temperature, use a large serving spoon to slide fritter batter into the hot fat in portions.
Fry for 2-3 minutes until golden brown on the bottom, then carefully flip each fritter.
Fry the other side for 2-3 minutes until golden brown all over, but do not allow them to become dark brown.
Remove fritters with a slotted spoon and drain on paper towels, then let them cool.
Mix powdered sugar, vanilla extract, and water in a small bowl until smooth and spreadable.
Brush the glaze over the entire surface of each fritter and let it dry, then flip and coat the underside as well.
Let the finished fritters cool completely on a wire rack until the glaze has hardened, then serve.