Bring home (or to the place you want to have your drink) the Daab... preferably ready for consumption.. ask your nariyal water man-- he can keep it ready for you to drink at home.....
once you are home (with all the other ingredients) open out the top of the Daab and pour in the vodka... as much as you want... after you have removed the corresponding amount of water from the Daab of course... ad in a few drops of the lemon juice and half a lemon.. the juice of course.. and drink with a straw.