Make the Dough
In a large bowl, combine the flour, sugar, yeast, and salt.
Add warm milk, eggs, and butter. Mix until a dough forms.
Knead by hand or with a mixer for 8–10 minutes until smooth and elastic.
Cover and let rise in a warm place for 1–1½ hours, or until doubled in size.
Prepare the Filling
Melt butter in a skillet over medium heat.
Add diced apples, brown sugar, and cinnamon. Cook for 5–7 minutes until apples soften and sugar melts into a syrup. Cool completely before using.
Assemble the Babka
Roll the dough into a rectangle about 10×14 inches.
Spread the apple cinnamon filling evenly over the surface.
Roll the dough tightly into a log, then slice it lengthwise into two long strips.
Twist the strips together, keeping the cut sides facing up.
Place in a greased loaf pan and let rise for 30–40 minutes.
Bake and Glaze
Preheat oven to 350°F (175°C).
Bake for 35–40 minutes, covering loosely with foil halfway if it browns too quickly.
While it bakes, make the syrup by heating sugar and water until dissolved.
Brush the hot loaf with syrup as soon as it comes out of the oven.