what is the best practices for sandbox database

We are currently working for a booking website and there are many partners that can integrate with our website via REST APIs. We need to give our partner a test environment during the integration process and we have three suggestions

1- Create the testing booking and production booking on the same database and the same table with different number formats. ( like add T letter before the booking number)

2- Create a different table for the testing booking.

3- Both testing and production bookings in the same table and the same format but with a flag to distinguish the testing booking. Please advise us with the most correct solution or if there is another solution.