If you actually expect me to answer this seriously, then I have to say "Why in the world are we discussing this nonsense? Does it even matter if it's a sandwich or not? It doesn't change the reason for eating it!"
But since this is a meme, I'm not going to answer this seriously. No, a hotdog is not a sandwich. However, there are exceptions to this rule. If you're eating at a beach or in a desert or something like that, and then you accidentally drop it in the sand, it magically becomes a sandwich. However, there also is an exception to that. If you have placed your hotdog in the fridge for over 30 minutes it's actually a coldcat in a hotdog disguise, and if you then drop it in the sand it doesn't magically become a sandwich because the exception above counts for hotdogs, but not coldcats. Coldcats become sandwiches if they fall in a children's sand pit, but hotdogs don't. I'm not sure what happens if you put a coldcat in the microwave before dropping it in the sand though. It... Uh...
...Look, it's very complicated, okay? I had to read a 60 page long book just about this topic in elemantary school, I can't remember every detail described in that book! And I don't care enough to go and look it up again, so just... Just use the internet or something!