If a member donates money to a cooperative C corporation would the cooperative corporation have to include that as taxable income?

The bottom line answer here is ... it depends.  Was the contribution made as a capital contribution to join the Co-op?  Was it a fee to join?  Was it just a contribution from a non-member for a charitable purpose?  Is the Co-op subject to Subchapter T of the Internal Revenue Code?  Does the Co-op file form 1028?

If the contribution was a capital contribution then the answer is no to taxability.  If it was a fee then yes.  If it was a contribution with no other purpose than to contribute then also yes.  The background on your question does not provide enough detail for a definitive answer but I believe the above 3 circumstances should assist you in your answer.

Subchapter T and how money flows through a Co-op

About Form 1028 per IRS

@linda-gospelhill