Beat egg whites until foamy in a large glass or metal mixing bowl until stiff peaks form. Lift your beater or whisk straight up: the egg whites should form a sharp peak that holds its shape.
Beat the egg yolks, sugar, butter, and milk together in a large bowl. Stir in the pineapple and bread. Lightly fold egg whites into the pineapple mixture, then spread the mixture into a large baking dish.
Bake in the preheated oven until golden brown, 35 to 45 minutes.
