I've always been highly skeptical of the idea that juice can actually short out an auto battery. In order to short the battery out, juice would have to be highly conducive. If juice was highly conductive then the standard heated coil technology of ecigs wouldn't work, because the juice would be shorting out the coil.
If that theoretical stuff doesn't convince you, then consider this. Take a multimeter and test the resistance/conductivity of juice. I have, it doesn't even register, meaning juice is non-conductive for all intents and purposes that are vaping related.
What juice CAN do is clog up the auto switch rendering an auto battery inoperative. 99% Iso alcohol (common rubbing alcohol available at supermarkets and pharmacies) is also non-conductive. (also personally tested)
Soak the battery in 99% alcohol, this should dislodge and remove any juice inside the battery. Then let it dry for awhile, luckily alcohol evaporates quickly.