To share files with your customers and work on documents together, use an Anyone link in Microsoft 365
From your SharePoint site, select the folder you want to share
click Share, and then click the link settings button.
In the Link Settings window, make sure Anyone is selected. If this option is grayed out, it needs to be turned on in the SharePoint admin center.
Optionally, select the Allow editing checkbox and enter an expiration date for the link.
Click Apply.
In the Send Link window, enter your customer's email address, type a message, and click Send.
Your customer will receive an email with your message and a link to your files.