I honestly wouldn't, it's not going to make you look any more attractive as a candidate. I would just go there to have fun and see what it's like. It's not supposed to be something stressful or testing of you candidacy. Also, I would show up as a high school kid, not as a ridgid this is where I have to be I am not here to have fun pre-midshipman. Nobody is judging you here. A "joe" is apparently someone who shows up just a little too rigid and determined to the point that they look fake and are not fun to be around. If you're not there to have fun there, the plebes probably won't want you there next year cause they're not looking for a joe, they're looking for a fun motivated candidate, its a really good time my visit was a lot of fun.
As a recent grad, I'm going to respectfully disagree with this point of view. Bringing a care package for the plebes does not make you a "joe" at all. Trust me, you'll quickly learn what a "joe" is when you get to the Academy.
I wouldn't arrive at your candidate visit weekend trying to impress people with your knowledge of the military or anything to that effect, but there is absolutely no harm in bringing your plebe guide some junk food. I definitely would have appreciated it from my candidate. In most cases, the plebes are volunteering to lead you around, so it's always nice to show them your appreciation.