Are you sure it's just water in their ears? If the ear is red and has an odor, it could be an ear infection. There's medicine on the market that you can squeeze into the ear, massage it and then, as the dog shakes it's head, clean out the debris that comes up, with a cotton ball.
It could be that when you hosed them, water got in the ears and then began to dislodge the infection that was already in there. You don't say how long the dogs have been shaking their ears but generally, after an hour or so, if it's just water, they stop shaking their heads. If it continues, it might be something else.
Either way, ear infections in dogs are pretty easy to get rid of. Yes, you can use apple cider vinegar mixed with equal parts of water, and put a couple of drops in each ear, using an eye dropper. Message the ear from the bottom of the ear in order to dislodge the clog.
There's a lot of info about canine ear infections on the internet. You should search out canine ear infections and their causes and treatments to get a better idea of what to do in the future.
Good luck :)