Azure B2B - Azure B2B helps the company to invite members of other organizations to share their application access. Just you need to share with your collaboration. It will also provide a security policy.
Azure B2C - The main difference is that it is not used by single organizations. It is built to allow anyone to sign up as a user with their credentials. It is an independent service for building a consumer application.
I hope this will work.
Want to know more? Read the blog on Azure certification now!!