There's kosher, then there's kosher for Passover. Kosher for Passover indicates that the rules governing the absence of leven (i.e. yeast) have been closely followed.
If a food/drink vendor in Israel wants any business at all during Passover, he must display some type of signage that indicates proper observance of the rules on any machines that dispense food or drinks. It's helpful if said products also have some type of clear labeling regarding Passover observance.
Usually signs appear more official than the one above, which seems to have been created on a home computer. It lacks any official stamps or names of rabbinic authorities, but seems to have done the trick because I saw several patrons look at it before purchasing items from the machine in the picture below. You can see the kosher sign on the top right hand corner of the machine.