Put the sugar in a pan with 2 tablespoons of water. Gently heat while stirring, then simmer for 10-15 minutes to thicken. Cool, then stir in half the lime juice (this can be made 3-4 days in advance; chill until needed).
Put the quinoa and coconut milk in a pan with 375ml (13fl oz) of water. Simmer for 20 minutes until almost all the liquid is absorbed. Stir in the ginger, lime zest and honey, to taste.
Toast the coconut in a frying pan on high heat for 2-3 minutes.
Serve the pudding topped with the pineapple, some syrup and coconut. If you like, serve with lime wedges.