Short answer: No. You do not need to add Sheetgo to your SPF record.
When Sheetgo sends emails on your behalf, it uses the Gmail API (or Microsoft/Dropbox equivalents, depending on your sign-in). This means emails are delivered directly from your own Google Workspace account, using Google’s authorized mail servers. Because of this, the messages are already covered by your existing SPF configuration, typically:
v=spf1 include:_spf.google.com ~all
Sheetgo does not send email from its own mail servers, nor does it act as an external SMTP sender. Instead, it simply triggers your email provider to send the message as if you had sent it yourself. As a result, no additional SPF records or DNS changes are required.
If you use DKIM or DMARC, your existing Google Workspace setup continues to apply normally.
In summary:
You do not need to include Sheetgo in your SPF records. All authentication is handled by your email provider because messages are sent through your own account.