make use of twilio’s totp [time based one time password] and push authentications using authy app and apps script for your web app.
In this example script from sourabh choraria you can find out how you can use Twilio’s Authy service with a Google Apps Script Web App. Authy allows you to implement time based one time password authentication for your web app removing the need for username/password management
Source: use twilio’s authy with google apps script web app
Member of Google Developers Experts Program for Google Workspace (Google Apps Script) and interested in supporting Google Workspace Devs.