Brahm Ji,
Thanks for your input.Last sentence from you is complete in itself if we ignore the actual context of it being "jootha".
I have a point to make here - What one considers "jootha" is actually something that has already been used/consumed by someone else. So if we don't use "someone else", that will be uncertain of it being "jootha".
A product already consumed by self is not considered "jootha".
So, still in my opinion, the correct sentence could be:
I will not eat this banana as it has already been eaten by someone else.
Still open to further discussion please.