My nearly 8 mth old DS has had a really bad time for the last three weeks with teething and croup.
During this period he started waking at 9.30 wanting a feed (in addition to all his usual feeds later in the night). I was giving him this while he was sick and cranky.
Now he's better and the tooth is through he is still waking for it so a few nights ago I decided to try the cooled water.
The first night he woke, I didn't pick him up but gave him a bit of a suck on a bottle of cooled water while he lay in the cot. He went straight back to sleep.
The second night he was having none of it, and screamed as soon as the bottle was in his mouth. So I took him out and gave him a quick breastfeed in the dark. He went back to sleep.
The third night he stirred a bit and started grumbling at 9.30 - I offered him the water but he didn't want it, so I popped his dummy in and he went back to sleep.
Last night he did not stir or wake at all until after midnight

So I think it's worth trying but it may take a few days and a bit of perserverance before they get the message.