why does my battery completly drain down when parked for only two weeks.

Sparks can happen when hooking up a cable no matter what you do. First, test the "new" battery to ensure it has a full charge and can sustain a load. Once that's there, you'll need to perform a parasitic draw test if the "loss of power" happens without starting the vehicle and running it over a period of time. See this article for more information on that: https://repairpal.com/parasitic-drain-diagnosis Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops