Beat sugar, oil, eggs, and vanilla. Add apple with dry ingredients and mix well. Spray a two pound coffee can with cooking spray or grease and flour it well. Pour batter into can, filling no more than 2/3 full. Place can in crock pot. Do not add water. Cover but leave cover ajar so steam can escape. Cook on high 3 1/2 to 4 hours. Don't peek before the last hour of baking. Cake is done when top is set. Let stand in can a few minutes before tipping pudding out on a plate. Serve half-rounds plain, with whipped topping, or a pudding sauce.