Milk is one. Egg Yolk is another. There are lots of liquids out there.
Now this one may seem real gross, but I will suggest it. Blood.
I feed my dogs raw (raw meat, bones, and eggs) and routinely trick them into eating things with blood. If you can handle it, they (from my experience) love it! Any meat packed container from your grocery store (sliced beef heart from Walmart has the most) will contain alot of blood. It's rich in smell and taste.
I may seem like a nut now, but I swear it works.
