Parts of my job are sleep inducing - like sitting watching filtrates dripping for up to 3 hours! I usually plug my mp3 player in and listen to something loud on these occasions but it doesn't always stop me from slipping into micro-sleep/daydream mode.
The worst thing for me though is working in a room with no windows - the lack of daylight makes me (and many of my colleagues) constantly tired - a bit like having year-round SAD.