You would need a letter from your company (Just ask the HR dept., they already have the form).
Run-alone to QDC and produce this letter along with your ID card and a down-payment of 1000/- Qar is needed. They would take your snap and produce you with a card and you are free to shop for the amount that the person will decide behind the counter..!!
Happy drinking... But please, DON'T drink & drive..!