Preheat a griddle over medium-high heat.
Slice each cinnamon bun in half lengthwise. (Works best when the cinnamon buns are slightly stale.) In a shallow baking dish or pie plate, whisk together the eggs, milk, and vanilla. Dip the rolls into the egg mixture, flipping to coat completely. Cook on the griddle until golden brown on both sides, about 2 minutes per side.
In a small bowl, whisk together the frosting and molasses and add enough warm water to create a pourable syrup consistency. Arrange on serving plate and drizzle with the warm syrup.