I make these at home all the time. Toasted muffin, bit of butter and mayo, bacon, over-easy egg, a few drops of Sriracha. Heaven on a plate.
One I used to make years ago: Toasted bagel, cream cheese, thinly sliced red onion, smoked salmon, tomato and bacon.
Our most common quick portable breakfast like this isn’t a sandwich, per se - it’s more like a pizza. Pita covered with ajvar, and then a layer of cheese, melted in the toaster oven. Top it with a crispy fried egg, some smoked paprika, and a dash of Penzey’s Fox Point. I’m sure it could be reimagined as a sandwich, but I like it the way it is.