Preheat oven to 375 degrees. GENEROUSLY spray muffin tin with cooking spray, set aside.
In a large bowl, add the brownie mix, oil, water, and eggs. Stir 50 strokes until combined. Fill 12 muffin tin slots 3/4 of the way full. Bake 22-25 minutes until a toothpick inserted into the center comes out mostly clean.
Place tin on a wired rack for 10 minutes to cool slightly. Using the round end of a utensil, gently press in the tops of the brownies to form cups. Transfer brownies to the wires rack directly to cool completely.
Once brownies are cooled all the way, pipe in the frosting. Top with half a strawberry and sprinkles, if desired.