I am on Level 45 now and I don't know if this is a bug, but whenever I attempt to give my increasingly angry group a soda, Karma won't go over to the group! If I click on a parking space, she'll run over with the soda bottle hovering over her head, but then when I click the group, one of their cars will show up but she won't come over...
 
is there a special spot that I am missing? I keep restarting the level, because of this...
 
also I can't figure out if the radio station is connected to their patience in anyway? when I change the song it doesn't seem to have any effect.. but why does the green button glare the way it does???
 
'sigh' -- I am wondering of this game was smart to get.. it doesn't seem to allow me to be great like the other dash games!! =)

I initially had problems getting Karma to delivery the snacks. Sometimes she sould not go to the customer area no matter where I clicked. One FAQ I read stated you have to click on the first customer in line. But sometimes the car would appear instead of Karma delivering the snacks.
Below is a summary of how I get it to work. Example based on Level 1.6
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Once you want Karma to delivery the snacks, click on the vending machine. Notice that a ‘1” check mark box will appear on the vending machine. Karma will walk over to the machine.  Wait until Karma stands in front of the machine before you make your next mouse click. To deliver snacks to the customers dropping off their car, locate the first person in line (bottom row rightmost person).  Click just above the first person’s right shoulder. A ‘1’ check box should appear on the customer waiting area. On Flo’s dinner level, this check mark box appears on the stone sidewalk to the parking lot. Notice that when Karma is walking to the waiting area there is a snack carton over her head. If you don’t see the snack carton try to click on the vending machine again.
For customers picking up their cars. Same idea. The first person is on the bottom row left. Click just above the left shoulder.  The check box for the customers waiting to pick up their cars is located on the right hand side just below the driveway. If you don't see this checkbox Karma will not walk over there.
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As far as the radio it does not effect the customers. According to the game help: "If the green light is flashing that means Karma is getting tired of the current radio station. Switch the station for a boost of speed."