In this article Jahswill Essien describes how to use Google Sheets with Flutter via Google Apps Script.

This article assumes the following:

• You have experience using the basics of Flutter and can call APIs and read an existing codebase
• You have little to no understanding of Google Apps Script
• You have some experience using Google Sheets or spreadsheets in general

I’m sure many of you reading this post will already be familiar with Google Apps Script and have little/no experience deploying Flutter apps but I also know a lot of Google Apps Script developers are keen to try new stuff.

If deploying mobile apps is a thing that interests you I’d highly recommend also looking at Google no/low code development platform, AppSheet, which enables you to quickly create/deploy apps often using Google Sheets as a backend. If, however, you need custom graphics or pixel perfect UI, solutions like Flutter would be my personal starting point. Enjoy!

Source: How to use Flutter with Google Sheets, Apps Script, and Codemagic | Codemagic Blog