As of now, it's only possible to push Assets data from production when you copy all of Jira's data into your sandbox. This is as informed in  What data is copied to sandboxes.

Especially now that Assets is expanding to integrate with products other than JSM, you may want to copy Assets to the sandbox without impacting Jira projects already in it.

This suggestion is to have the ability to copy Assets data to the sandbox as a separate product.