Combine the soy sauce, brown sugar, butter or margarine, mustard and water and heat until the sugar and butter dissolve. Let mixture cool and pour over wings. Marinate in the refrigerator for 2 hours, turning occasionally.
Preheat oven to 350 degrees F (175 degrees C).
Bake chicken wings in marinade for 45 minutes, turning once and spooning marinade over chicken occasionally. Drain on paper towels and serve.