ice

Warning, don't try to eat these ice cubes, as they're made of stone and will be very painful to remove once they make their way through your digestive track.

Sure, it could be planking. But (a) her head doesn't appear to face straight down and (b) she's a little overdressed for planking. So we'll go with the "needs a place to cool down after a long night" theory.

It's not worth your gin and tonic being cold if it's going to hurt you!