I seen this on 1 of those commercial tips on the golf channel and it is a great tip to help hit the ball straighter whether you struggle with a slice or hook.

If you slice place the water bottle just outside and behind the ball and make sure you dont hit the water bottle. The only way to not hit the bottle is to make sure your swing is coming from the inside.

For a hook you put the bottle between you and the ball and make sure you are swinging a little over the top to avoid hitting the bottle. (not 100% sure on this one, haven't tested the anti hook)

I havent tried it yet but i did something similar with a box last summer to help me start swinging from the inside more and it has helped where my misses now are left. If i hit it right it is usually a push with my higher irons (8,9, and wedges) which i dont get since my swing feels like its coming from the inside. Maybe i am standing too close...

Anyways i think it is a good tip to get you swinging em' straigher.

I agree it's a great tip, but i was watching the same thing you were and the guy hit the ball before putting the bottle there and they showed a down the line shot. Once he put the bottle there, his path was so far off, he either pull hooked it, or sliced it off the range from the look of the down the line angle. while it might be a great drill, i think there's a lot of variation as to where you put the bottle. Too much to be really effective on a hook problem.

i found this too one of Vijays tips to hit a slight fade, and make sure you are not coming from the inside too much.

http://www.golftipsmag.com/instruction/golf-tip/tip-of-the-week/vijay-drill-21108.html

I get what you are saying there are a lot of variations of where you put the water bottle. I know though that when i had the box behind me it helped me realize what it felt like to come from the inside, something i never really grasped until then. As far as the super over the top swings i think it is a really helpful tip and can help people hit it much straighter (or alteast not right) since it forces you to come from the inside.I think the drill could be helpful once you know where to put the water bottle.