Start the rice cooking according to the packet instructions.
Meanwhile, heat the oil in a large frying pan over a medium heat. Fry the onion for 5 minutes until soft and beginning to colour, then add the garlic and curry powder and cook for 1 minute until fragrant.
Tip in the pilchards with all of their tomato sauce. Half fill one of the empty tins with water, swirl it around and pour that in too.
Break the pilchards into large chunks with a wooden spoon. Stir in the sugar and simmer gently for 10 minutes until the sauce is dark, thick and glossy.
Taste and season, then serve the curry over the drained rice.