Cut the cheese into cubes of the same size. Divide the iceberg lettuce into leaves. Rinse under cold running water and spin dry. Then cut or pluck the leaves into bite-sized pieces. Wash, drain and cut grapes in half. Remove the stones from the pulp with a sharp knife. Mix a marinade out of the oil and vinegar and season with sea salt, pepper and sugar. Arrange the iceberg lettuce on plates. Mix the cheese cubes and halved grapes, place on top and drizzle with the vinaigrette.