Regarding Vernon: the deck I beat him with during testing contained all cards obtained in the intro except for Mutual Gaining and Raid the Pantry (don't forget to equip Keep Pumping after beating Tom). If you beat Tom as efficiently as possible, that is to say end up at least anywhere below 30 Wgt (not necessarily using the same deck as for Vernon), and have a lot of luck against Vernon, you'll eventually get it. That said, he isn't meant to be beaten, and as such, I don't plan on locking any significant events behind achieving that. The dialogue already has some variance at several places though, including one of the new storylines added in 0.4
For now, there aren't any plans to add other methods of gaining Odious Zest.
The energy drink material drop was bugged in the initial release of 0.4.0. There's already an updated build on Patreon that fixes it, which should also restore the item in saves where you've already beaten him.