I have seen this and wanted to try it. i'll have to pick it up! I love everything grapefruit lately. Picked up a Grapefruit rum a few weeks ago, it was ok. I think i prefer vodka!
Equal parts vodka, fresh squeezed grapefruit juice, st germain. Top with club soda. I warn you-- it goes down too easy. Worst hangover o had in a few years when I had a few too many.