Nature has a way of providing an observable metric.

Let me correct my statement. Given no alternatives, cockroaches will eat anything without a caloric deficit. Hence my statement about wallpaper paste. A true infestation of cockraoches will eat anything that will sustain the intrusion. If there is no available “food” around, cockroaches will crawl over cucumbers to eat the paste holding the wallpaper to the wall.

So long as there is no additional sugar in the brine (hence calories), the roaches will not eat the pickles.