Thank you for providing clarification to your needs. I think I understand this request as trying to keep local clocks in sync to match the time used by Google CloudSQL. Please let me know if my understanding is wrong.
As you may already know, all Google Cloud Applications and APIs use the same NTP server time source including Cloud Functions, Cloud SQL, Datastore, BigTable, BigQuery, and DataFlow.
So, if indeed your target is to ensure that your Local Clocks are in sync with the same NTP Server, I believe you can find instructions about the required configurations here[1].
For more information about the Google Public NTP Servers, I found these articles[2][3] interesting and I think they may be helpful to guide your thoughts.