on the rocks

A term for a beverage (usually liquor) served over ice without added water or other mixer.

1.  Ruined, spoiled, as in Six months after the wedding, their marriage was on the rocks. This expression, alluding to a ship running aground on rocks and breaking apart, has been used figuratively for other disasters since the late 1800s.
2.  Served over ice only, as in He always drinks whiskey on the rocks. The "rocks" here are the ice cubes. [Mid-1900s]
3.  Destitute, bankrupt, as in Can I borrow next month's rent? I'm on the rocks. This usage, from the late 1800s, is heard more often in Britain than America.