2 cups warm water (between 105 and 110 F)
2 ounces active dry yeast
3/4 cup sweetened condensed milk
1/2 cup vegetable or canola oil
3/4 ounce salt
4 1/2 pounds bread (high-gluten) flour
1/2 cup (1 stick) unsalted butter, melted and divided
1 1/3 cups lightly packed dark brown sugar, divided
3 tablespoons ground cinnamon, divided
3 cups powdered sugar
1 1/2 teaspoons pure vanilla extract
1/2 cup milk
Purple, Gold, and Green Colored Sanding Sugar (available at specialty baking stores)
Preheat oven to 350 F and line 2 baking sheet pans with parchment paper.
Combine water and yeast in the bowl of a standing mixer and stir with a whisk. Let stand for 5 minutes. With the dough hook attachment, turn the mixer on low and add the condensed milk. Once combined, add the oil and salt. Add the flour, 1 cup at a time, until a soft dough forms. Continue mixing the dough at low speed until smooth and elastic (about 8 minutes). Dough will still feel sticky at this stage.
Place dough in a large bowl, coated well with cooking spray or additional vegetable oil. Turn the dough in the bowl to coat all sides with the cooking spray. Cover with plastic wrap or a tea towel and let rise in a warm place (85%), free from drafts, for 1 hour or until doubled in size. (Gently press 2 fingers into dough. If indentation remains, dough has risen enough.)
Divide dough into 2 equal portions. On a lightly greased surface, roll each portion into a 18 x 10-inch rectangle. Brush the top side of each dough with the melted butter. Sprinkle evenly with the brown sugar and cinnamon. Beginning at long sides, roll up dough, jellyroll style and pinch to seal the edges. Gently twist the ends of each roll in the opposite direction and arrange in a circle on prepared baking sheets. Pinch the edges of each circle closed. Cover both loaves loosely with well-greased plastic wrap or lightly floured tea towel and let rise in a warm place (85%), free from drafts, for 35 minutes or until doubled in size.
Uncover loaves and bake at 350 F for 20 to 25 minutes or until the crust is lightly brown. Allow bread to cool completely on top and bottom before icing.
Whisk together powdered sugar and vanilla. Add milk gradually, using enough until icing is pourable but still rather stiff. Spoon evenly over each cooled bread until well coated. Sprinkle evenly with colored sugars in desired pattern.