For the pork: Combine the coriander, lime juice, oil, chilli powder, garlic and onions in a large dish. Add the pork slices and turn to coat. Preheat a grill on medium-high heat.
For the red slaw: Combine the cabbage, coriander, oil, vinegar, chilli powder, bell peppers, red onions and 1/4 teaspoon each salt and pepper in a large bowl. Toss to mix and set aside.
Remove the pork from the marinade and discard the remaining marinade. Sprinkle the pork on both sides with 1/4 teaspoon each salt and pepper. Grill, turning once, until browned and still a little rosy inside, about 10 minutes. Transfer to a large plate.
Grill the tortillas, turning once, until grill marks appear and the tortillas are softened, about 1 minute. Transfer two tortillas per plate. Divide the pork and a little slaw among the tortillas. Serve with lime wedges.
Evenly divide the pineapple among four bowls, top each with 1/4 cup sour cream, 1/2 tablespoon sugar and a sprinkle of cinnamon. Serve with the pork tacos.