Had some issues with larger, heavier drinks wanting to tilt forward due to the slight angle of the seat adjustment handle. I wedged some pool noodle foam I had from another project
between the handle and the holder. Works great now, up to the large size Whataburger cup.
The thing I like best is the holder is not some obvious or clunky thing attached to the car. Pretty much hidden from view, but there when you need it.
Still working on the Jack Daniels solution, but it is fine for the 1L Tequila Cazadores Blanco (round bottle) or the new Carta Blanca "Caguamon". Warning: These have not been fully tested under emergency braking......
Good luck,
Clay