How to Make It
Preheat oven to 350°F. Coat a 10-cup bundt pan generously with cooking spray.
Combine butter, sugars, corn syrup, and cinnamon in a saucepan over medium. Cook, stirring often, until butter melts, sugar is dissolved, and mixture is smooth, about 2 minutes.
Pour 1/2 cup of the sugar mixture evenly in bottom of prepared bundt pan. Place half of the donuts evenly in pan; drizzle 3/4 cup sugar mixture over top. Repeat layers with remaining donuts and sugar mixture. Bake in preheated oven until heated through, about 20 minutes. Place pan on a wire rack, and cool for 5 minutes. Invert bundt pan onto a serving plate.
Whisk together powdered sugar, milk, and vanilla in a medium bowl until smooth, 1 to 2 minutes. Drizzle glaze over top of donut monkey bread.