What is NOT considered an additional form of communication for sponsors?

In the context of sponsor communications, internal social networks, email, and intranet are all tools primarily utilized for communication within an organization or between stakeholders involved in a project. These platforms foster collaboration, provide updates, and facilitate information sharing within a defined audience, which is critical for executing an effective sponsorship and ensuring that all parties are aligned.

External websites, however, serve a different role. They are typically not exclusive to internal communications, as they allow for broader outreach to the public or external audiences. While they can contain information relevant to sponsors, they function as platforms for organization-wide messaging, brand promotion, and engagement with a wider audience beyond internal stakeholders.

Thus, external websites do not fit the mold of an "additional form of communication for sponsors" in the same way that internal tools do, making it the correct choice in this question.