That made me curious. "Self", I said to myself when I read this, "why not try it? How bad could it be?" So this morning we tried it out.
We start with a bowl of cereal.
Add some coffee (low acidity coffee blend, a medium grind pour-over at 1:13 extraction).
How will it taste?
It tasted... Not bad at all. Quite good in fact.
When we were kids a long time ago, our grandmother would sometimes make us a treat by shredding a cinnamon roll into a large mug, then mix in coffee, milk and sugar. This is amazingly delicious (and I believe my brother still makes it for himself from time to time).
Mixing coffee and cereal is really the same kind of idea. It's not nearly as sweet, and you don't have the cinnamon and cardamon flavors from the rolls, of course. Instead you retain a lot more flavor from the coffee itself. Ritsuko feels this mix might be better still with an espresso rather than drip coffee; it would give you a stronger coffee flavor. I feel it was quite good already.
If I moved somewhere and was told that this is how we eat breakfast around here, I would have no problem having this every morning. I do feel that it's a waste of coffee — I prefer to enjoy it sans sugar and roasted carbohydrates if I can — but if you don't care then this is not bad. And if you are short on time, you could grab a mug of coffee and cereal on your way out and have a decent breakfast on the way to work.
Coffee and cereal does work well together. Live and learn.