Sharing a Single File in Another Department Group/Team

Hi

Client uses SharePoint online group or teams sites like a Department Structure or File Share

Example. Finance uses in finance, HR users in HR and General that all staff will have access to

Lets say for whatever reason a single file now needs to be shared with a staff member in another Teams Site , how can this be handled

Example : Single file in Finance Teams/Group  needs to be shared with a user in Sales Teams that is not a member of the Finance ?

Group Permissions are only generally only  used for this client