Grease 8 oz. microwave safe mug or ramekin. Set aside.
In a one cup measuring cup or small mixing bowl, whisk together the dry ingredients (flour, sugar, cocoa, baking soda and salt).
Add vinegar, oil and water and whisk until smooth. Make sure there is no dry flour remaining at the bottom of the cup. Use spatula if needed to make sure all of the ingredients are combined into one smooth batter.
Pour the batter into the prepared mug or ramekin. Sprinkle 1 tablespoon of chocolate chips over the top.
Place mug in microwave and cook for 1 minute. Check the cake. If there is a spot in the center that looks uncooked, cook cake for 15 more seconds. Check again and add 10 seconds, if needed. Check cake with a toothpick in a few places.
Sprinkle remaining chocolate chips over the top of hot cake, cover with inverted small plate or lid (if using a ramekin) and let sit until the chocolate melts. Spread with a back of a spoon or small spatula. Add sprinkles. Let the cake cool slightly. Serve.
Notes
This recipe is perfect for 8 oz. mug or ramekin. It can be easily doubled or tripled to make more serving.
You can drop a caramel-filled chocolate square in the center of the batter just before cooking for a sweet surprise. Keep that in mind when checking the cake for doneness.
Please note, that the nutrition value can vary depending on what product you use. The information below is an estimate. Always use calorie counter you are familiar with.