"Hello XXXX, I am Brian with JABE Vending and we are working with the National Children's Cancer Society.
Basically what we are doing, is going around to local (businesses love the local word) businesses in the area and asking them to donate as little as 1 sq foot of space so we can place a small gumball/candy machine.
In addtion, note that this is at no cost to you. I will fully service and stock the machines for you."
That is the main gist of it. Then answer a few questions they might have, like liability etc.
If I get even a stutter or a slight pause, being a salesmen like I am - I go in for it. I waste no time and get to the chase.
But hey, that's me =)