If you want to send a SendGrid email when you add new Firebase child records, you can do that using Zapier.
You will need:
To link your Firebase to SendGrid, you must have an active SendGrid account. To learn more about getting started with SendGrid basics, start here. For more information about getting started with SendGrid on Zapier, go here.
Now test the Zap to make sure it works. Once you’re satisfied with the results, new child records created in Firebase will send corresponding emails in SendGrid.
If you ever want to change this Firebase and SendGrid integration, just go to your Zapier dashboard and tweak anything you'd like.