Preheat oven to 325 degrees and line a cupcake tin with papers.
In a large bowl, stir together brownie mix, eggs, vegetable oil, and water until just combined, taking care not to over-mix.
Fill cupcake papers a little more than ¾ of the way full.
Bake for 27-29 minutes until a toothpick inserted into the center of a cupcake comes out clean. Let rest in tins for a few minutes before moving to a wire rack to cool completely.
When cooled, frost cupcakes if desired.