In a shallow dish, whisk together eggs, milk, vanilla, and cinnamon until combined. Working one slice at a time, dip bread until fully soaked, 45 seconds.

In a separate bowl, add Fruity Pebbles. Transfer soaked bread to Fruity Pebbles and press to coat. (Use your hands if necessary.)

In a large skillet over medium-low heat, melt 2 tablespoons butter. Add French toast and cook 3 minutes per side. Repeat with remaining butter and slices.

Serve with whipped cream.