To make acar, combine the water, vinegar, sugar, eschalots, chillies, turmeric and ginger in a medium-sized saucepan. Bring to the boil, reduce the heat to low and simmer for 3 mins. Add the carrot and apple, remove from the heat and allow to cool. Season with salt and pepper.
Place the vermicelli in a bowl of water and allow to stand for 10-15 mins or until soft. Drain immediately and toss through the coriander leaves and the sesame oil.
Season the fish fillets with salt and pepper. Heat the oil in a heavy-based frying pan and cook the fish in batches 2-3 minutes each side until golden and just cooked when tested. Serve the fish fillets with the vermicelli and top with the acar.