Prepare a 9-by-13-inch baking pan by lightly spraying it with cooking spray.

In a large saucepan, combine the brown rice syrup and peanut butter over medium heat. Stir frequently for about 5 minutes until the mixture is warmed and liquefied.

Remove the pan from heat and add the vanilla extract and protein powder. Stir vigorously until fully incorporated.

Quickly fold in the rice cereal with a spatula until all pieces are coated in the peanut butter blend.

Transfer the coated mixture into the prepared pan, using the back of a spatula to press it evenly and firmly.

Place the pan in the refrigerator for at least 1 hour to allow the treats to set. Cut into 18 equal squares.