to find the density of heiniken beer you have to drink three bottles of the beer. Then you have weigh yourself, and divide your weight by the weight of the beer. Multiply that number by pi, and then divide by 2. that is the density.
If you find in beer some tasting ingredients besides the water, then beer must weigh slightly more. One of the "ingredients" is alcohol, which weighs less than water, so depending on the exact mix, it may weigh more or less.
Yes you would weigh about a pound more. But something quite interesting is that a fluid ounce of water or beer does not weigh one ounce, it is slightly more. Exactly how much more depends on wether you use imperial or U.S. units.