Google sheet script that will add two menu items, so you can import / export between Sheets and Firebase
Accompanying sample sheet can be found here: https://docs.google.com/spreadsheets/d/1XgK3XVURmHPvq0jzkmaNos4Pm_wfN17KfRXBXm7IoQM/edit?usp=sharing
Alternatively you can use the sample-data.csv in this repo and import that into your sheet
For more information checkout the blog post at https://liftcodeplay.com/2020/02/08/exporting-and-importing-data-to-from-firestore-using-google-sheets/