Battery problems

I own a 2000 GMC Sierra and when the truck sits for 2 days, the battery dies. When i take the battery wire off, sparks come out & it's drawing power from somewhere. Has anyone had this problem before?

You need to start by finding out what is drawing the power. Use a test light or volt meter disconnect the neg battery cable and put the meter or the light between the two and start pulling fuses 1 at a time to see if the light goes out or dims, or volts change. The clock radio will always draw power to retain memory. If you have added a stereo system or other accessories I would start with them, someone may have hooked a power wire to a constant power and should have been hooked up to a switch power.