The battery should be disposed away, but I took it to play. Deep discharged lead-acid batteries can become damaged, but if the battery has zero volts, it's sure it is irreversibly damaged.
The first step to play with it was to revive it in some way. I used my variable power supply and adjusted it to around 15 volts, and applied that voltage to the battery through a 1W 150 ohms resistor.
