How can I make breadcrumbs without a full, yeast-leavened loaf of bread? What's the best (fastest, most efficient) way to make breadcrumbs from scratch, without having any old bread?

I'm curious if there's something quick I can do, when I realize I want 5 cups of breadcrumbs and have no old bread, and don't want to buy or bake a loaf of bread just to immediately pulverize it.

That is, what is the fastest, simplest, easiest bread-like thing one could make, which would turn into breadcrumbs in a food processor?

One more edit: I didn't really intend this to be asking "what other ready-made things can I buy (or have around) and turn into breadcrumb substitutes". I want to know, at the very least, the best way to streamline the process of making and drying bread given the fact that I don't care if it's ever moist enough to eat as bread, and don't care about its overall shape or texture or anything else we usually care about in bread.
Three substitutes come to mind:


Saltine Crackers 
Pretzels 
Select brands of Cereal (Chex, Corn Flakes, etc.)


Take these for a spin in your food processor till you reach the consistency you desire.

Depending on your ultimate goal one or any of these could serve as a suitable sub for "bread crumbs"