If you have users who are to take part in Fleetcoach training but don't have an email address then a simple option to consider is establishing a new Gmail account and then using multiple aliases for your users.
Using email address aliases means your Gmail account will receive email sent to firstname.lastname@example.org.
For example, messages sent to email@example.com and firstname.lastname@example.org will both be received by email@example.com.
To send Fleetcoach invitations to these users simply use the firstname.lastname@example.org format for the email addresses in the Fleetcoach 'Invite users' form.
When the email is received at email@example.com you can distinguish which Fleetcoach invitation email is for which user by looking at the 'To:' field of the message. This will contain the full email alias used in the message (e.g., firstname.lastname@example.org).
Using this method you need only create one new email address that can be used for all your users who don't have an email address of their own.
Step one: Set up a gmail account, e.g., email@example.com
Step two: Send Fleetcoach invites as normal, to e.g., firstname.lastname@example.org
Step three: The email@example.com email address will receive all the emails.