I spray every meat that I smoke (except meatloaf) with a mix of 3 parts apple juice and 1 part bourbon. I spray every 45 mins to an hour, when I need to add wood chunks to keep up the smoke. The sugars in the mix carmelize, turn brown, and add to the "bark" on the outside of the meat, especially pork butts and briskets.
Hope this helps.
Take care, have fun, and do good!