To clear data in your Odoo SH testing branch without deleting the branch, consider using the "Demo Data" module or similar extensions. This module allows you to reset or clear specific data (invoices, stock, manufacturing orders) while keeping your branch intact. Consult the Odoo documentation or community for detailed guidance.

You can open shell on odoo.sh (your_branch.dev.odoo.com/odoo-sh/webshell/ws).

You could try to delete the database with psql.

psql​​

drop database "your_database_name";