Add the Cap'n Crunch and corn flakes to a large zip-top bag and crush with a rolling pin into coarse crumbs. Pour into a shallow bowl.
In a second shallow bowl, whisk the flour with the onion powder, garlic powder, salt, and pepper. In a third bowl, whisk the eggs with the milk.
Dredge each tender in the seasoned flour, then the egg wash, then press firmly into the cereal crumbs to coat all sides.
Heat about 2 inches of oil to 325–350°F. Fry the tenders in small batches for 3–5 minutes, until golden and the internal temperature reaches 165°F. Don't crowd the pot.
Drain on a wire rack set over a baking sheet.
Air Fryer: Air fry breaded tenders at 400°F for 10–12 minutes, flipping halfway, until 165°F. Oven: Bake at 400°F on a greased rack for 18–22 minutes, until 165°F.
Whisk together all the dipping sauce ingredients and chill 15–30 minutes. Serve the chicken hot with the Creole mustard sauce.