If I go there with an empty flask. Will I be able to get inside with it? I mean empty, nothing on it. I wont use it at all in the night club

Use a paper cup to drink out of on ur way over and toss it out before u enter!

Very unlikely, and even if you get it in secretly, they'll certainly kick you out if they see you with it.

Rly ? My plan was to drink on the way there x.x didnt expect and empty flask to be a problem

At best, no.

rairu..likely not. at best you may be able to cloak room it.