I don't know how anyone ever manages to find a seat at Mein Haus am See, but Z-Bar is a great,…read morequieter alternative just down the street. Thanks to its movie nights and location in Mitte, it attracts a bit of a hipster clientele. But rest assured that you won't have to put up with any hipster pretentiousness here.
Most cocktails run the gamut of €5-7, which I feel like is pretty reasonable for Mitte. I have no problem dropping €5.50 on a gin and tonic or €6.50 on an Old Fashioned, though I might be a bit biased coming from San Francisco. I thought that the bartenders were friendly enough by Berlin standards -- I appreciated how he asked if I had any gin preferences so I wouldn't end up paying for an expensive G&T with Bombay Sapphire. Dark and smoky (while not overly so, those sensitive to cigarette smoke might want to think twice about enjoying a few libations here), Z-Bar is a very laidback and artsy bar that I'd recommend to anyone who wants to have a conversation with their friends over a few drinks.