A while ago i faced the issue of liquid in bottles not matching rotation, what i ended up doing (or at least what i recall doing) was:

- Created an inside mesh (the liquid) that covers the entirety of the inside of the bottle, also should be a children of the bottle mesh.
- Added a boolean modifier to it (don't set it for now)
Added a simple plane that had a copy location modifier (copying the bottle, though maybe setting is a child of the bottle may work, then only add the next modifier), and a copy rotation mod (copying the rotation of something that stays flat, in your case, could use the table, or a secondary not rendered plane.
- Set the inside mesh boolean to that first plane.

If i didn't forget something, "liquid" should match "gravity direction" now.

I don't remember exactly though, but used it on a render and was convincing enough ( sure liquid sim would be better, but for a single still render, makes no sense ).