That looks like an excellent drink! I’m impressed the studio strobes stopped the liquid that well. Mine flash too long, so I use Canon Speedlites instead for that sort of thing. Good looking photo!
How much reflection you desire can affect choice of materials. This stuff has less reflection but it is cheap enough and you don’t have to worry about it breaking and cutting you. http://www.homedepot.com/p/Husky-6-ft-x-100-ft-Black-6-mil-Plastic-Sheeting-CF0606B/202184211. If you want a little more reflection, you can place some Saran Wrap over it. Setting it up as a miniature seamless in a shallow pan, you can put a thin film of water over it, which will be reflective once the ripples stop. This works best with items that can stand water.
Black Plexiglas is nice but scratches easily, is stiff, and relatively expensive. Painting glass never occurred to me.