what is the best way to recondition my car battery?

I am trying to recondition my battery reconditioning training when i measure it, it reads 12.5v but doesn't have enough Amps to turn over the engine. when i charge it it works fine but after i shut the car off i cant start the car back up again the alternator works fine. if i pour out the acid and pour in water mixed with baking soda shake the battery around empty it and pour fresh acid in work?