Whisk together the eggs, milk, and pina colada mix in a bowl. Heat a skillet over medium heat; melt butter in the skillet until the foam disappears. Soak the bread slices in the egg mixture, turning the slices over a couple of times.
Gently lay the soaked bread slices into the hot skillet 2 at a time and pan-fry until the french toast is golden brown, about 2 minutes per side. Transfer cooked french toast slices to a warmed platter while you finish cooking. Top each 2-slice serving with several slices of banana to serve.
