the rule of thumb is 4 servings of water per serving of alcohol... a beer is 12 oz, so, 28 oz of h2o per beer should keep you in pretty good shape. the anti-fitness factor of beer (or alcoholic drinks in general) is that it soaks up the fat --> glycogen enzymes, so anything past one or two drinks, the alcohol uses up all the alcohol dehydrogenase your body has, and turns all the alcohol direectly into fat. e.g. beer belly. anyway, on an hour-long ride (or more) you burned at least 500 calories. a beer has about 120. have fun.