The investors have asked for a business plan, what should I do?

When I ask anybody to close their eyes and imagine what a business plan is, everybody has a very different idea of what it should be, ranging all the way from a sketch on the back of a napkin to a printed and bound manuscript so big and heavy that would hurt if you dropped it on your foot.

A photo of a toy doll of the superhero Dead Pool posing before his own smart phone on a selfie stick, throwing a peace sign with his free hand.
You might need to portray your startup in the best possible light but how much detail should a business plan include, and when does it become a work of speculative fiction? (Photo by Mulyadi on Unsplash)