Punchpass offers a custom link that you can use to tie an external training or nutrition plan to a customer's record. So, you can set up a custom plan for a customer in an online tool (such as Google Docs, Dropbox, etc), & add the link to that plan to the customer's account.
In the customer's Info tab, click Edit Info to add the document to the Custom Link field.
This gives you a lot of flexibility with the design of your training or nutrition plan. Many web-based document storage tools will allow you to share directly with your customers too, so you and your customer can both view and/or update the doc ongoing (if that's what you want to do).
To find the shareable link for a Google Doc or Spreadsheet, go into the document and click File =>Share. Click the green circle to copy the shareable link. You can then paste this link directly into the Custom Link field in Punchpass.
You should also consider the additional share settings so you can potentially share the link with your customer. You can adjust the settings to reflect whether others can view or edit the document.
Make sure you click "Done" to save your changes.
You can also store a PDF (or another image) file in Google Drive and use Punchpass' custom link field to take you right to the file from a customer's record.