This question looks similar to Using flakes in a mash, but is not actually the same. I was thinking, if someone runs out of maize flakes, and definitely wants to use some for his mash, what happens if he uses corn flakes? Anyone can see that they are not just maize flakes, but also contain other nutrients, some of them actually being sugars, but are the flakes themselves fermentable? In the same spirit, around my place they sell some rice crackers that are not actually baked, but are more like rice popcorn pressed into cracker form. What happens if someone uses these?
If you use corn meal, you'll need to do a cereal mash to gelatinize the starches before adding it to the mash. I tend to use instant grits or polenta so you can skip the cereal mash. At one of our club's Iron Brewer contests, I made breakfast cereal the secret ingredient. The contestants got cocoa puffs, Fruit Loops, a cinnamon wheat cereal, and Lucky Charms to use in their beers. Post fermentation you couldn't really detect any of the character of the cereals used.
In one of the Basic Brewing Radio podcasts I listened to recently, John Palmer mentioned making an American lager with "corn meal right off the shelf" as an adjunct.
If I were in a pinch, I'd rather use corn meal than a breakfast cereal, which has dozens of ingredients, including butylated hydroxytoluene.
On the other hand, actually making applejack with Apple Jacks® could be fun. And what better way to get that characteristic fruity, estery aroma into your ESB than Froot Loops®?
(In case it sounds like I'm being sarcastic, I'm not. An ESB "dry-hopped" with Froot Loops® sounds like just the thing to stick it to people who take their beer too seriously.)
I did a Grape Nuts triple last year at 9.42% which was awesome. The cereal was in the mash and the characteristics were evident when poured. Awesome aroma. I used two boxes. I'm making an IPA today with two boxes of Golden Crisp. Very excited about that.