The "Bulldog Pass" punch card has 4 punchable areas for bathroom and drink breaks.
Each 9 weeks I give my students a new punch pass to keep in their folders. When they need to leave the room (at an appropriate time) they bring their punch pass up, punch their card and leave it by me until they return. That way if there is a fire drill I easily know if someone is out of the room. Each new 9 weeks they receive a new pass.
You can give these out to the whole class or just your "frequent flyers". It has done WONDERS with the constant questions of "Can I get a drink...Can I go to the bathroom?"
it is in .doc format so you can change the picture to whatever you want.