I don't think it's a bad idea to give water in the morning, as I usually give 8 oz in the morning. Even then, most of the dogs won't drink all of it as there have been countless times I've found left over water in the bowl that night before work. After the workout, that is the time the dog needs the water the most. Most of the weight a dog loses is water weight, and most dogs will lose at least 1lb of weight with a decent workout. Some dogs can lose more due to their intensity. The water is needed afterwards to get the body back up and running properly through digestion, waste removal, renal function, all that kind of thing that revolves around body systems.