Line an 8-inch x 8-inch baking pan with parchment paper. Set aside.
In a medium saucepan, warm the sweetened condensed milk over low heat. Add the sugar cookie mix and stir together until combined.
Add the white chocolate chips, butter, and vanilla. Stir until smooth.
Pour the fudge mixture into the prepared baking pan, spread it into an even layer, and top with sprinkles.
Let the fudge set up at room temperature or in the fridge for at least 4 hours, or overnight. Cut into 16 pieces (4x4 grid) or into your desired-sized squares.
Notes
Nutritional information will vary based on the size of the fudge squares.