The very best way is to poor the acid out of it. There's industrial (military) applications for batteries to sit for very long times and have power when needed. There is typically an automatic system that has two seperate chambers, one for acid, one for lead. On demand a valve opens and bingo, a fully charged battery.
I also remember motorcycle batteries being sold seperatly, battery and acid. There's all sorts of changing laws about handling and transporting lead-acid batteries and that was a technique to comply with some.