Mix together the soy sauce, tomato sauce, mustard and sugar and lightly brush over the sausages. Set aside.
Put the sultanas in a large bowl and sprinkle with 1 teaspoon of the lemon juice. Remove any discoloured leaves and the core from the cabbage, then finely shred the leaves and add to the bowl. Quarter, core and dice the apple, toss with the remaining lemon juice and add to the bowl. Coarsely grate the carrots, then add to the bowl.
Preheat a grill to a moderate heat. Mix together the mayonnaise and yoghurt, season, then stir into the coleslaw.
Cook the sausages on a foil-lined grill tray for 15 minutes, turning frequently until browned all over and cooked through. Remove the sausages and thickly slice.
Grill the pita breads for 1–2 minutes on each side. Cut them to make a pocket and spoon some coleslaw into each. Pack in the sausage slices and some more coleslaw and serve straight away. Serve any remaining coleslaw alongside.
• Take care when grilling the pita breads. They should be warm and steaming, but don't brown them or they will be difficult to split open. You could also warm the pita breads in the microwave oven or toaster. • Leftover coleslaw, covered in the refrigerator, will keep for 2–3 days. Use it as a tasty filling for sandwiches.