This is a paid asset, but now you can download Google Sheets For Unity Lite Free.
Detail this asset from Unity Store: Original Link
Google Sheets For Unity Lite v3.0.1 (Latest version)
“If possible, please buy the package to support the developer”
Google Sheets For Unity Lite (GSFU), enables the developer to handle game data from Google Drive Spreadsheets. This opens a world of posibilities for collaboratively development & design, simplifying the process of creating, handling, distributing, tweaking and importing data, among localized or distributed teams.
Note that this is the LITE version, for the full edition read more on this Unity forum thread.
GSFU enables the developer to save or fetch values from, and to Google Sheets at runtime or design time. This turns heavy duty tasks like game balancing, tweaking or localization, into an instant and pain-free procedure.
Check the API Reference.
• Save and receive data from google spreadsheets at runtime or design time.
• Customize your workflow with flexible and solid Google solutions for distributed work.
• Works with all plataforms, Desktop, Mobile and WebGL builds.
• No Google account credentials required on the Unity side.
• Source code included.
• No Google API or third party dependencies to maintain.
• Works with privately shared Google spreadsheets.
• Examples included.
• Simple & clean API included for simple needs.
Disclaimmer: This package requires intermediate to advanced programming skills in order to understand and use the asset for your own purposes.
Need more features? Learn more about the main edition here.