Preheat oven to 350 grease 1 bread pan. To make sour milk us 1 tablespoons of lemon juice or vinegar plus milk to make 1 cup. stir, Let sit for 5 minutes. Dissolve soda in milk and set aside Cream margarine and sugar, beat in eggs. Alternately add sour milk and flour to creamed mixture. Add vanilla and mix. fold in apples. Pour into greased pan. Spread topping on just before baking. Mix together the melted margarine, brown sugar, flour and cinnamon. Bake for about 1 hour.