Melt the butter in a skillet over medium heat until it foams and begins to bubble slightly.
Add the Cheerios and stir to coat them thoroughly in the melted butter.
Cook for 3-5 minutes, stirring occasionally, until the Cheerios turn golden and crispy.
Remove from the heat and immediately toss with the sugar and cinnamon until well combined.
Serve warm and enjoy the sweet, crispy delight.