This is how I made a Bloody Mary costume for Halloween. It was pretty easy, just some plastic sheeting, spray paint, sand (for the celery salt rim) and a few other things for the celery stalk, olive, etc.

Step 1:

First, the celery is a window shade that I found in the garage.

The olive and cheese are just painted Styrofoam blocks from walmart. The olive centers are actually the caps from the spray paint bottles. then I just jammed a dowel through it all.

Step 2:

After painting the plastic sheets red I folded them over on themselves to form the shape of a glass, make sure you account for the taper of the glass shape. It's all held together with zip ties.
My girlfriend was the beer chaser, that's why we made a cigarette, it made a good place to keep money and things.

You WILL get a lot of attention wherever you go, so be ready. ALSO, make sure you have a way to pee without taking the costume off. , I ended up just going out the bottom, while being careful