Make Google Sheets as your database for your web app or add-on developed in Apps Script without sharing the file. … In order to keep our database secret to end users we will use a Service Account (SA) … This Service Account is not a real account, no Gmail or Drive attached but a service account can access a spreadsheet. We will use this property to manage our data.
As the post author Stéphane Giron indicates before using Google Sheets as a database you need to fully scope out if it’s the right solution for you. For ‘small’ data you can often get away with using Sheets and in this post from Stéphane you can learn how to do it in a way where you can have access control by setting up and using a Service Account.