Soak the rice in lukewarm water for at least 1 hour so that the starch is precipitated and then rinse it. Boil it in about 1 litre water for 16 minutes and then leave it for another 10 minutes. In the meantime heat the apple vinegar a little until the added sugar and salt is melted. Pour it onto the hot rice and stir it until cool. The cold rice will receive a bit of a sour taste this way. Spray a 40-piece Zila cake mould abundantly with Tarant anti-stick spray and then push the prepared rice into the mould with damp hands. Apply medium force when pushing so that the rice will fill the gaps evenly. You can also spray your hands with the anti-stick margarine and this way the slightly sticky rice will not adhere to your hands. After filling place a metal plate on top of the rice to push it even, after turning the mould upside down this will make the base of the snacks. Let the filled rice stay and cool down in the mould. Turn it upside down and pull down the silicone mould carefully from the sushi rice, cut around and lift the metal frame. Along the marking lines cut the rice into triangle shape snacks and then coat them in the alga sheets that you can buy ready.