Maintaining awareness of the presence of colleagues can be difficult when collaboration is distributed across separate offices. In this paper we present CoasterMe, a situated desktop widget that leverages the natural behaviour of drinking to support informal awareness of a colleague's availability in the workplace. A pilot field trial showed that CoasterMe helped coworkers to build in-the-moment awareness of availability and supported an improved understanding of work routines, enhancing social coordination and preventing wasted effort. CoasterMe also created a sense of co-presence and connectedness by making users feel as if they are sharing a drink over distance.