How do I send webform submission data to a google sheet?
Right now the only available solution is to use Zapier.

Ivan Zugec did a great screencast showing How to Create Forms using Webform and Contact in Drupal 8 and includes a demo showing how to push webform submissions into a Google Sheet using Zapier.

Hopefully, someone will port the Webform to Google Docs module from D7 to D8.