is a hot dog a sandwich

You took the internet's oldest argument to a living, breathing coworker.

It depends who you ask, and the people who get the final say don't agree.

• No: The National Hot Dog and Sausage Council ruled in 2015 that a hot dog is not a sandwich. Its view is that the hot dog is its own thing. Merriam-Webster took the other side and said a hot dog does fit its definition of a sandwich.
• Legally, it depends where you are: The USDA has labeling rules for "sandwich-type" products and treats hot dogs as one. New York State's tax rules also count hot dogs as sandwiches. A 2006 Massachusetts court case (Panera v. Qdoba) said a burrito isn't a sandwich, and people often cite that reasoning to argue hot dogs aren't either.
• On structure: A sandwich is usually a filling between two separate pieces of bread. A hot dog bun is one piece hinged at the bottom, which puts it closer to a sub roll or a taco. Under the "cube rule" meme, a hot dog counts as a taco.
• What most people think: Polls tend to find most people say no.

Short answer: Technically you can argue it is one, but in everyday use it isn't. Call it a sandwich at a ballpark and see what happens.

Settled in the time it took you to ask someone.