Cats "drink" water by eating wet food mostly. Feeding them dry food in any capacity will hurt their kidneys. They aren't used to drinking because of it and even if they do, it usually isn't enough. Most of the materials I was given for fostering / adoption says to try to switch them to wetfood and keep them on it because of the reasons above.

As to your question - there are freeze dried meats that can be given to them, but because of the kidneys thing, you aren't supposed to give them more than a few cubes a day. Iirc 15 or 20?