Some random dude walked up to me while I was waiting outside a food place for my food and asked me this question.
I said “no, I dont give out random favors” and something along the lines of that’s sus.
Is it rude to say no to random dude that asks for a favor?
You’re mixing up two very different things. In your post you asked how you should respond in the general situation of someone asking if you could do them a favor, and so that’s the question that people answered on this page. But then in your replies you try to apply those answers to a totally different situation.
Here’s the answer to the question you asked, and then the answer to the question you were trying to ask:
BUT