In a large mixing bowl, whisk together the warm water, ½ cup sugar, oil, 2 eggs, salt, and ½ tsp cinnamon. Stir in 1 to 2 cups of the flour, then add the yeast. Gradually mix in enough remaining flour (about 5 cups total) to form a cohesive dough. Knead on a lightly floured surface or with a stand mixer for 8–10 minutes until smooth and elastic.

Shape the dough into a ball and place it in a greased bowl. Cover with a clean cloth and let rise in a warm spot for 45–60 minutes, or until doubled in size.

While the dough rises, toss the chopped apples, ¼ cup sugar, 1 tbsp cinnamon, and lemon juice together in a medium bowl. Set aside.

Punch down the risen dough to release air bubbles. On a lightly floured surface, roll the dough out into a large circle about ½-inch thick. Spread the apple mixture evenly over the surface. Fold the edges inward and gently knead/roll the dough into a large ball to enclose the filling. Let the dough rest for 5 minutes.

Grease a 10-inch springform pan and set it on a rimmed baking sheet to catch any drips. Using a sharp knife or bench scraper, cut the dough into random chunks. Arrange the pieces in the pan so the apples are evenly dispersed throughout, and top with any loose apple pieces left on your board.

Whisk the egg and 1 tsp sugar together, then brush the mixture gently over the top of the loaf. Sprinkle with coarse sugar if desired. Cover loosely with plastic wrap and let rise in a warm place until almost doubled in size (about 30–45 minutes).

Preheat your oven to 350F. Bake the challah on the middle rack for 45–55 minutes, until deep golden brown and cooked through. Cool in the pan for 10 minutes, then run a knife around the edges, remove the springform ring, and transfer the loaf to a wire rack to cool completely under a clean towel.