SaaS with exposed SQL

For a client I'm going to deliver a SaaS solution, SaaS in that matter it's still closed to a limited clients that has to sign a contract with us, so not shared world wide and the client base will be around 5-10 companies.

Our first client, the pilot client so to speak, has it as a requirement that they can perform SQL queries (read mode only) on the data, so they can make analysis in Excel along with what our application serves.

My question is that I would for maintain reasons prefer to serve everything in the same codebase, but I'm wondering how I can make sure, clients can access other clients SQL records?

I'm using Laravel so the solution for different installations would be to make everything in maintainable packages and upgrade all installations from there, but this can grow to a lot of work.

How to have the solution with only one solution I'm still not sure, maybe it is to have a separate database per client? That would require a central database to point them to the right database of course, or maybe only have some of the tables in another database, but it already sounds like a mess to me :-)