This is probably going to be a love it or leave it topic.
I tried using apple juice, wine, water and some weird combinations and finally gave up on the whole idea. My opinion is
it is just another expense that doesn't add much value to the finished product so I quit doing it and haven't looked back. I know some guys swear by it but I found I like my finshed product better when smoked "dry". I also found it made a mess in my smoker and even grew mold. My smoker is electric so that may be part of the problem but I also found that it took more energy (heat) to vaporize the liquid and when the liquid was gone the temperature would rise past my set point. In addition, I don't like the puddles of liquid that accumulate on the product especially fish.
I have a wood fired / charcoal .. smoker... I use a water pan every time I fire up my smoker!! I dont use any thing but water in the pan .... Just seems to keep the moistuer in better..... I'm not sure with electric smoker or not ... never used one ... but all wood / charcoal fired smokers are all diffrent ...... you just have to learn it and the modifications you due .... if any
I have a weber Smokey Mountain and never put water in the water pan, Just line it with foil for easy clean up. This brisket came out great when I smoked it last week. The moisture it adds to the air may help insulate the meat and keep the smoke from penetrating.