Preheat the oven to 325 degrees F. Generously grease a tube pan.
For the cake: in a large bowl, combine the sugar, eggs, oil, orange juice, flour, baking soda, salt, cinnamon and vanilla extract; and mix well. Fold apples, coconut, and pecans into batter.
Pour the batter into the prepared pan and bake until a tester comes out clean, about 1 1/2 hours.
Shortly before the cake is done, make the sauce: Melt the butter in a large saucepan, stir in the sugar, buttermilk, and baking soda, and bring to a good rolling boil, stirring constantly. Boil for 1 minute. Pour the sauce over the hot cake in the pan as soon as you remove it from the oven. Let stand 1 hour, then turn out onto a rack to cool completely.