Cook the breakfast sausage according to package directions. Drain any excess grease.
Prepare the eggs as desired (fried or scrambled).
Whisk together the maple syrup, Dijon mustard, and apple cider vinegar in a small bowl to make the glaze.
Lightly toast the halved croissants.
Assemble the sandwiches: Place a sausage patty (or link), egg, and cheese slice on the bottom half of each croissant. Drizzle generously with the maple mustard glaze.
Top with the other half of the croissant.
Serve immediately.
Notes
You can add a sprinkle of fresh chives or a few arugula leaves for an extra touch of flavor and color.