Throwing out candy they might or might not get if they behave. Perfect way to add uncertainty, fear and stress into situation. The initial situation is described as "irrational kids" who "cant absorb explaining".

And also, at least where I live, it is actually against road rules to throw away your crap out of window while you drive. It is kind of littering, except more dangerous as you are at speed.

consequences are natural and logical, not arbitrary, so children can reason and intuit about them.

Like not being able to hear the audiobook they are playing, or missing a turn or crashing the car due to distraction (don't do that).

If a behavior has no consequences and you need to invent punishment, why is the behavior wrong? Just because your personal preference trumps your kids?