Place strips of bacon on a cooling rack over a cookie sheet to collect drippings; Place in oven while preheating to 350F
While bacon is cooking, mix together milk, eggs, cinnamon, and vanilla extract into a 13×13 (or similar size) baking dish.
Mix 6 eggs in a bowl with salt until scrambled. Cook in the pan with butter on medium heat, stirring occasionally, until eggs are fully cooked and coagulated; about 5-7 minutes. Set eggs aside.
Heat up a pan with 2 tbsp butter. Place 2 bagel halves into french toast mix until fully soaked on each sides; about 1 minute.
Cook in the pan about 2 minutes on each side. Set aside; repeat step for additional bagel halves with an additional tbsp of butter as needed in the pan. Set bagels aside.
When the bacon is cooked, remove from the oven. Top bagel with eggs, cheese, and bacon. Place the sandwich in the oven on the cooling rack for about 5 minutes or until the cheese is melted. Let sit for a couple minutes and serve. Enjoy!