1. Using a potato peeler, carefully peel several strips from one of the fruits, slicing off any of the bitter, white pith on the underside. Cut the strips into fine julienne (this is an optional stage you can still make this dish without the strips of peel).
2. To make the caramel sauce, place the sugar in a saucepan with half of the water. Allow to dissolve slowly over a low heat and when fully dissolved, bring to the boil. Let it boil until it begins to turn a golden colour. Watch it carefully at this stage, and when it turns a deep caramel colour, pour in the rest of the water. Stand back, as it will fizz and sizzle quite violently. Stir until any lumps have disappeared, add the julienne strips of peel, then remove from the heat to cool.
3. Peel the ugli fruit, removing as much of the stringy white pith as possible. Turn on its side and slice into circles (not segments) and remove any pips. Place in a bowl and pour over the caramel sauce. Chill until ready to serve.