Can I release a single with one of CD Baby's Distribution Packages?

CD Baby's Distribution Bundles are for albums only. If you are interested in distributing a project that contains just a single track, you can sign up for digital distribution directly through CD Baby - https://cdbaby.com/cd-baby-cost.aspx

You can still purchase physical media for your single and can get started by creating and saving a quote here - https://duplication.cdbaby.com/Quoter/default.aspx