I rarely clean mine at all, unless they're acting up or tasting funny. When I do, I use hot (not boiling!) water straight from the tap. Then I let 'em soak a bit, and change the water a couple of times. Then I blow them out, and let them air-dry overnight, or pop them in a 150 - 170 F oven for 20 or 30 mins (if I'm in a hurry).
The
juice is water-soluble. No need for alcohol or anything fancy. I have only killed atty's by abusing them with high-voltage (now I use HV atty's for that), doing "dry burns" to remove the shipping fluid, and other bad ideas I read about on these forums (one guy recommended using CLR!!! Crazy!).

Other than that, mine usually last a month or more. As cheap as they are to replace, that's good enough for me.
[...] but i thinking to add directly the liquid to the atty.[...]
We call that "direct dripping" on the forums, and it works great if you have a "manual battery" with a button you press. If it is an automatic with a hole in the center of the connector, then it is not sealed and
juice can get into the battery and ruin it. What type do you have?