Preheat your barbecue for direct heat (coals arranged in a bank in the middle or high if using a gas barbecue). See Notes for grilling/alternative cooking instructions for both the chicken and pineapple.
Pat the chicken dry with kitchen paper, then put in a large freezer bag or sealable container. Finely grind the salt and pepper and 1 tsp of the sugar in a pestle and mortar. Add the garlic granules, 1 tsp paprika, the thyme, oregano and cayenne pepper, then grind again until fine. Add to the freezer bag/container, then seal and shake to coat the chicken in the spices. Leave to marinate at room temperature for 10 minutes or up to one day (see Notes).
Add the chilli to the pestle and mortar with the remaining 5 tsp of sugar and 1 tsp of paprika. Grind together to make a paste, then brush the mixture over the pineapple wedges to coat. Leave to marinate for 15 minutes or up to one day (see Notes).
Remove the chicken from the bag/container. Brush with the oil, then arrange over indirect heat (at the edge of the barbecue) for 20 to 30 minutes, turning regularly, until crisp and the juices run clear when the thickest part is pierced with a skewer (a probe thermometer should read 70-72C). Remove the cooked chicken to a platter or tray and cover loosely to keep warm.
Brush the pineapple with a little oil, then cook it over direct heat (in the middle of the barbecue) for 2 to 3 minutes on each side until charred and sticky. Serve with the chicken. Garnish the chicken and pineapple with the torn coriander.