Add a bit of sweetened condensed milk along with eggs, oil, water, and whatever else your recipe calls for to your batter to give it a rich, milky flavor and extra sweetness.
You’ll have to experiment with how much sweetened condensed milk works with your mix. Aim for a batter thick enough to pour, but not as thin as pancake batter.
You can also take tips from the condensed milk can to make a simple tres leches cake, or make Russian buttercream frosting with sweetened condensed milk and butter.