In a microwave-safe bowl, microwave 1 cup apricot nectar on high for 50-60 seconds or until hot. Dissolve gelatin in hot nectar. Set aside to cool.
In a large bowl, combine remaining apricot nectar and enough water to measure 1-1/4 cups. Whisk in pudding mix and milk powder for 1-2 minutes. Let stand for 2 minutes or until soft-set. Whisk in cooled gelatin. Fold in whipped topping and cake.
Pour into an 11-in x 7-inch dish. Refrigerate for 2-4 hours. Garnish with apricot slices.