Was told by a Dunkin Donuts worker that I can’t bring in my dog because it’s not kosher.

So I’m just gonna say that I’m NOT mad at the Dunkin’ Donuts worker for telling me this. I’m just here to ask…I thought kosher was about food only? I mean does it also apply to the place that is selling kosher food? I didn’t plan on staying inside because I have a huge dog. I just made a quick stop to get some iced coffee. I don’t usually go to this DD because I have another one closer to me, but I was walking my dog so I had to make do. Thinking about it now…my local DD is also kosher, but I’m never told anything about bringing in my dog. Also yes I tried googling this, but everything is so confusing and I needed clear cut verification. Thanks guys!