Bread soaked in milk to get them used to the taste, once they 'twig' they'll guzzle the milk right down. Mine love cow's milk, whey, cream, anything dairy.
I worked on a farm in Wales once where they used skimmed milk as part of the choox diet. The farm grew oats so all stock ate oats, but as oats are apparently a little low in protein for hens the milk made up the difference. And of course gave calcium for egg shells too.