In a mixing bowl, combine the diced apple, celery, pickled cucumber, shredded cabbage coleslaw mix, mayonnaise and seeded mustard. Mix well to ensure the sauce is coating all the salad items.
Put half the olive oil in a pan and put the inner side of the rolls down and cook on a medium heat until crunchy and golden, then remove and set aside.
Add the rest of the olive oil to the pan and place the German Bratwursts in and cook – turning regularly on a medium heat for 10-15 minutes and hot in the centre.
Remove the sausages from the pan and slice on a diagonal (you should get about 6 slices per sausage).
Take the toasted ciabatta and spoon equal quantities of the coleslaw mix onto each piece of bread then scatter the rocket across the sandwiches. Top with three slices of bratwurst on each sandwich and enjoy!