 It depends on exactly what they are doing. Everyone can be an asshole or snap. It's literally a problem with everyone, and I completely understand it.

 While I'm not an asshole myself? I'm more quiet and distant when I don't have caffeine. People who know me tend to pick up on that, because I am normally happy-go-lucky, and automatically assume I'm being a dick. I've legit had 30 people say that, including exes, because they expect me to be smiling and energetic all the time. Or talkative. 

 I worked as a "Barista" for years. Remember caffeine is a drug that you do withdrawal from, and that is understandable while someone isn't the same. I've seen people who are the nicest perk up when they drink it five minute later.

 So I don't usually take it personal. After working in the service industry my whole life I've learned it's normal. Even the nicest people become assholes and snap a bit. Not to mention the shit they are going through. 

 The key thing I look out for in someone snapping is an apology later. We are all human, and different. We all have our bad days, and I super appreciate it when someone apologizes about their behavior the next time I've seen them. You'd be surprised on how many apologies I've had weeks or months later. The way I see it is that people reflect and understood they took shit out on someone innocent.