Place two-thirds of the spinach in a 4-qt. salad bowl. Sprinkle with half of the sugar, pepper and salt. Top with eggs, ham and remaining spinach. Sprinkle with remaining sugar, pepper and salt. Arrange onion slices on top.
In a large bowl, combine the dressing mix, mayonnaise and sour cream. Spread over onions. Sprinkle with cheese and bacon. Refrigerate until serving.