[Neo Karls]

https://sampwiki.blast.hk/wiki/SetVehicleHealth
Try setting the value of health to a large value.

You need to get the Vehicle id(Plate) to destroy the cars that you have spawned
it will be like this

example:-

pawn Код:

new CreatedCars[100];

if the createdcar vehicle id is stored

pawn Код:

CMD:destroycars(playerid, params[])
      for(new i = 0; i < sizeof(CreatedCars); i++) {
        if(CreatedCars[i] != INVALID_VEHICLE_ID) {
            DestroyVehicle(CreatedCars[i]);
            CreatedCars[i] = INVALID_VEHICLE_ID;
        }
    }
    SendClientMessageEx(playerid, COLOR_GREY, "   Created vehicles destroyed!");
    return 1;

here is example of lock system
http://pastebin.com/f104e7ce2