Surely the definition of emptier is simply you can take every coin from the machine, leaving it empty.
Something you can manipulate to get a few jackpots is not an emptier (if it then stops you getting more out), although a low floated machine might run out of cash and 'go empty'.
So
1. No
2. Yes, but if it's already empty, what's the point
3. Yes, but what's the difference between this and 2?
Examples
1. Vamp it Up
2. Donkey Kong
3. ?