Beat sugar, oil, eggs, and vanilla.
Add apple with dry ingredients and mix well.
Spray a two pound tin 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.