Well you can use Meguiar's Quick Detailer spray or Mothers Speed Shine spray(both are included in their clay bar packages they sell)plus you can use either of those for inbetween waxing to keep your car shiney or to remove things like bird bombs,etc. and I believe even soapy water in a spray bottle but don't quote me on the last one.The above mentioned items can be purchased at most auto parts stores or even in the Walmart auto section.Others may have more items that you can try and use.
I've heard of people just using water alone but they keep the water clean and coming constantly so it is slippery. I'd just go out and buy the Mothers detailing spray or something similar. (Mothers smells like Cinnamon...mmmmm
ClayBar is designed to be used with a lubricant. The lubricant creates a "slick" surface for Z-18 ClayBar to glide across. In a spray bottle, mix ½ a cap of Z-7 Car Wash to 16 ounces of water for a lubricant.