Tired and Testy on the Clock

I work nights at this tiny deli that opens up early to serve morning coffee. Last night, I was behind a customer who just wanted to pick up some eggs and bread for their breakfast before heading off to work themselves. This is fine, right? It's not like it takes much time. Thing is, this person has been here a couple times in the last week. Each time, they ask about ingredients or products we don't even stock. I explain every single time. And each night it gets harder and harder to keep smiling when explaining things again. So there I was, doing my job, trying to be helpful as usual. They asked if we have gluten-free toast available for their breakfast sandwich. Now, this place? It's a convenience store on the cheap side. We don't even serve made-to-order stuff, let alone cater to specific dietary needs like that. I was so tired from my shift and already starting to feel groggy at two am. I told them with as much kindness as I could muster, 'Sorry, we do not carry gluten-free options here. Maybe try the supermarket down the street?' They gave me a look, like I had just kicked their puppy or something. But here's what gets me, they came back about half an hour later. Same story, more annoyed this time because I had closed for my break by then and another worker was helping them out. She told them pretty much the same thing, even mentioned our deli doesn't do custom orders at all. So yeah, I was tired and short-tempered. But I still tried to be as patient as possible when they came back after getting their answer from someone else who said no too. After that, I just couldn’t stay in my head about it anymore. It's exhausting being the one with all the answers at two in the morning. I'm not proud of lashing out or anything, but honestly? Being on that shift for a week straight makes me cranky and short-tempered. People have no idea what goes into keeping places open 24/7.