No that is not true. Assuming you exercise as much for cardiovascular health as burning calories, you should drink water after your workout. Besides, water (the old school kind out of tap, not that new kind of water with all sorts of vitamins and crap) doesn’t have calories, so it shouldn’t ruin your workout, at all. Even if you eat, and eat as many calories as you burned, you would still get the cardiovascular benefit, which is key.