Mix ingredients in a bowl and microwave for 75-90 seconds. (Using your mixing utensil or a knife, you'll probably want to cut the apple slices in the pie filling in half.)
Depending on the size of your bowl, you may have to finish the last 15-20 seconds in 5-second intervals to avoid overflow. The center should still be slightly moist but cooked.
If your cake sticks to the bowl, you may try mixing the cake in a bowl and transferring the batter to a separate bowl you've sprayed with nonstick cooking spray before going in the microwave.
Top with a bit more caramel syrup, low-calorie ice cream, fat-free whipped topping, or other toppings of your choice.
Notes
One mug cake has 5 Smart Points.
If your cake is too dry, you can try adding a bit more apple sauce, reducing the cook time, or reducing the protein to 1/2 scoop.