Shred apples in a food processor using the shredding disc. Place in a large bowl and mix in liqueur. Cover and refrigerate for 1 hour.
In a large bowl, whisk together flour, potato starch and salt. In a second large bowl, Beat together water, oil and eggs. Slowly mix liquid into the flour mixture. Drain apples and add to the egg and flour mixture.
In a large nonstick skillet, heat the oil over medium-high heat until shimmering. Place 1/4 cupfuls of the latke mixture into the skillet. Press down lightly. Sauté until nicely browned, about 2 to 3 minutes per side. Place on baking sheet lined with paper towels to drain. Repeat with remaining mixture.
Sprinkle with cinnamon sugar before serving.