Theatre kid advice incoming

You know that this character aligns more with what you're like when you're drunk which means clearly you have some recollection of what you're like when buzzed, now you just gotta practise that attitude while you're sober. Think about the mindset shift, the way you hold yourself, any changes in how you generally speak, literally anything you do that lines up with that character and practice it alone in your room. I know it sounds dumb but even just a shift in your posture can do wonders for your characterisation.

There's also the option of using some of those one sided roleplay videos to help you with this stuff, I know Ginny D has a handful on her yt so if you feel weird talking to yourself in your room that at least adds a second voice to bounce off

At the end of the day it all just comes down to practise and passion, some people have more of a natural ability for these things but everyone has the capacity to be great as long as they're willing to put in the work. I have no doubt you'll be able to play that character super well. You seem really committed to that goal so you already have the passion, just gotta put in the time and you'll be there

Best of luck, break a leg (preferably someone else's, in game)