Combine water and sugar in a small bowl. Add yeast and let stand until foamy, about 10 minutes. Add rice and stir well. Cover with plastic wrap and leave at room temperature, about 10 minutes.
Lightly mash the rice mixture, leaving some grains intact. Stir in eggs, raisins, salt, vanilla extract, cinnamon, and nutmeg. Mix in flour and cashews until well incorporated. Cover and let rise in a warm place for 1 hour.
Heat enough oil in a large saucepan to cover the beignets. Drop spoonfuls of batter into the hot oil; cook until browned, turning once, about 5 minutes. Drain on paper towels. Promptly sprinkle with confectioners' sugar.
