As a root user, when you create accounts for your customers, use their active emails on the account creation or from the API calls.
With the emails, you can easily reset passwords, if you forget your login password. It is the only way to retrieve the password.
If the client has a registered contact email on the SonicPanel, they can use the reset password link on the login page.
If the client does not have a registered email on the SonicPanel, you may contact your radio hosting provider to change it.