Pour the granulated sugar into a small bowl and set aside.
In a large bowl, combine the cake mix, eggs, sweetened condensed milk, and melted butter. Mix until the dough is smooth.
Chill the dough in the fridge for about an hour, or until chilled enough to roll. While chilling, preheat your oven to 350°F and line a baking sheet with parchment paper.
Scoop the chilled dough with a small cookie scoop, roll into balls, and roll them in the granulated sugar. Repeat with all the cookies, and space the dough a few inches apart on the baking sheet.
Bake for 11-13 minutes.