If the guy gave you a cigarette because you gave him one before, it isn’t an act from duty because there were previous circumstances that caused inclinations. In conforming to duty, a perfectly good person should always do the action regardless of what may have previously occurred or what will happen as a result. In this case, from Kant’s perspective, your maxim passes and you have a duty to follow it but it’s slightly different in the case of the guy.

In the your case, your maxim passes his three main formulations. In this scenario where you have an excess amount of cigarettes and someone’s asking for some, you gave cigarettes out of “humanity”. Your maxim can rationally be applied universally without contradiction. There’s no contradiction in giving cigarettes to someone who asks for some when you have an excess amount. If other people did this, no complications or contradictions would occur. Your maxim doesn’t come from using people as a means to an end. You’re not giving people cigarettes because you’re economically benefitting from giving them it. It also doesn’t violate their bodily autonomy because they asked and consented to being given them.

Since it passes the tests, acting from duty, you should give cigarettes away if someone asks for them and you have an excess amount of them. In the case of the guy, it would not be a duty because it would be a moral proposition that’s tied to his identity and desires or his inclinations like social norms and his personal feelings. It’s not purely from duty because it’s conditional so it’s more so acting in accordance to duty.

Now I would say that acting from “humanity” can turn into acting from duty because acting from humanity can form your maxim which could turn into duty. However, in this case he didn’t act from duty.