Preheat the oven to 180c 350fPlace sugar on a plate.Thinly slice the apples using a mandolin slicer, then press the apples into the sugar so it coats both sides then place on a lined baking tray.Place in the oven for 10 minutes, remove the tray and gently flip the apples over to cook the underside. NOTE the sugar will have become hot so be careful it doesn't burn your fingers. flip them using a knife. Place tray back in the oven for another 10 minutes until crispy. carefully remove from baking tray and place apple slices on cooling rack. You can turn the trays every 5 minutes so they brown evenly.