A single 12-16oz serving of 4-6% ABV beer is probably fine, has some good carbs from the barley and/or other grains and is not really diuretic if it's only the one since the total amount of alcohol consumed will likely not cause fluid loss beyond the volume of fluid in the beer. Probably not specifically beneficial though. Also has a relatively high amount of calories per unit of fluid.

Don't go thinking that tying on a buzz after every workout is going to be doing you any favors though because at that point the beer starts having more pronounced diuretic effects which is not good for muscle growth and the alcohol itself has negative effects on your growth hormones.