To use ModularSensors to publish to a new endpoint, the “best” way to do it would be to create a new publisher, set the format there, and push it to the library. There is documentation on how the ModularSensors library works here: https://envirodiy.github.io/ModularSensors/index.html
As far as posting to SQL, you can’t do that directly, at least not that I’m aware of. There’s not a way to send a raw SQL query over TCP-IP. Generally, you would use HTML on top of TCP to send a post request to a HTTP server which will make the SQL query via a PHP script. You have to set up that in-between step. TinyGSM, which ModularSensors uses under the hood for all internet connection, only creates the TCP link. If you look again at the EnviroDIYPublisher.cpp, you’ll see that the HTML POST request format for MonitorMW is all created manually there.
I’m sorry, I hope that that’s not too much alphabet soup for you to follow.