Put someone up 和 Drop in 的差別在哪裡？如果不好說明，請提供一些例句。

I have to admit, I'm not sure about "put you up," I'd need more context on the conversation.
"Drop in" means to go see the person anytime with out an appointment or letting them know that you're coming by. The phrase "Drop in appointment" is commonly used by businesses like hair salons where you can get a service done without making an appointment first.