Place the flour, salt, sugar, baking powder and cinnamon in a bowl. Add the water, oil and eggs and mix quickly with a fork. Transfer the dough onto a floured work surface and knead with your hands until you have a smooth, brownish dough. Let it rise in a floured bowl covered with a cloth until it has doubled in volume. When risen, take small pieces of the dough and make little cylindrical rolls about 15cm long. Join the ends together to form a doughnut shape and fry in hot oil until golden brown on both sides. Drain on absorbent paper and when cool sprinkle with icing sugar.