If the copy of the database is not going to have any of its own original data, then you have a couple of options.
- You could copy over a backup of the main database and restore the secondary database overwriting the data with current data on a regular basis
- You can create an SSIS package to export the data to flat files. The package can run on a schedule and you can sneakernet (as you have stated the two do not have any network connectivity) the files over to the secondary database. Another SSIS package or even a bcp job can import the data in