Can I bring a wooden walking stick as part of my costume? Also, I was wanting to tie a metal cup to my belt. Can I pour my purchased water/alcohol in it after purchase? I see others drinking from theirs. What are the rules on that?

Yes to both questions

As far as I know, all of that is fine. What you do after buying your drink is up to you, if you want to pour it in another cup, go for it. I've seen many people walking with staves, so I'm sure that's fine as well.

Basically no unsheathed weapons, and probably no outside alcohol allowed in