Create a new Google Sheet using a service account and share it with a human Google account so it appears in their Drive.

Documented steps

1. POST https://sheets.googleapis.com/v4/spreadsheets with OAuth scope https://www.googleapis.com/auth/spreadsheets (or drive.file/drive); body: {"properties": {"title": "My Sheet"}}. Response includes spreadsheetId and properties.title.
2. The created file is owned by the service account and lives in the SA's own Drive; it is invisible to any human account (not even in 'Shared with me') until you explicitly grant a permission on it.
3. POST https://www.googleapis.com/drive/v3/files/{fileId}/permissions with OAuth scope https://www.googleapis.com/auth/drive.file (or https://www.googleapis.com/auth/drive); fileId is the spreadsheetId from step 1.
4. Request body: {"type": "user", "role": "writer", "emailAddress": "person@example.com"}. Use role "reader" for view-only, or type "anyone" (omit emailAddress) for a link-shareable file.
5. Response returns the new permission's id and role; confirm this succeeded before handing the spreadsheetId to a human, since without it the URL returns a permission-denied page for that user.
6. Docs: https://developers.google.com/workspace/sheets/api/reference/rest/v4/spreadsheets/create | https://developers.google.com/workspace/drive/api/guides/manage-sharing | https://developers.google.com/workspace/sheets/api/limits