The most common use I've heard of for Coroplast -- not that I've done this, it sounds a bit rickety for the task, TBH -- is to use it for the body of a homemade velomobile.
For those not in the know -- a velomobile, more common in Europe than USA by far, is basically an enclosed bike or trike. Some have electric motors or other pedal-assist equipment, some do not. Google Images is your friend here ;)