You can get this on the Akenash's Atrium 2/4 level. As you're on your way to get the airship timetable, you get a prompt stating you can poison guards by having your clone poison food or water. So before you enter the room where you got the prompt, bring up your clone (
+
) and then move to the right of the room where the fruit is, puke (
) in the fruit and then hide under the desk.
Now just wait for the first and then second guard to die.
EDIT: You don't need your clone, you can puke
in the fruit bowl, too.
Bloop - 15GS!