Preheat oven to 350°F (175°C) and coat a 9×13-inch glass pan with cooking spray.
Mix brownie mix, vegetable oil, water, and eggs in a large bowl.
Stir exactly 50 strokes until the batter is combined.
Spread batter evenly in the prepared pan.
Bake for 28–31 minutes or until a toothpick inserted in the center comes out clean.
Cool brownies for about 10 minutes.
Break warm brownies into a large bowl.
Chop crème de menthe thins roughly.
Add chopped mint thins to the warm brownie pieces.
Stir until the heat melts the mint pieces slightly and everything is well combined.
Shape mixture into 1½-inch balls, pressing firmly.
Chill balls for 20 minutes in the refrigerator.
Melt chocolate chips and coconut oil in the microwave in 30-second intervals.
Stir after each interval until smooth and fully melted.
Dip each brownie ball into the melted chocolate, turning with a fork to coat.
Lift truffles and let excess chocolate drip off.
Transfer dipped truffles to a parchment-lined tray.
Add sprinkles on top, if desired.
Refrigerate for 5 minutes or let sit for 20 minutes until chocolate sets.