I have use the bar soap trick & I can tall you it works.
Around here, they use a mining pick, or a Halligan tool instead of a drill. It is louder, but quicker, plus it makes a bigger hole that drains the fuel much faster. No bar of soap or self-tapping screw is going to fix that.
I carry a small, 1/2 gallon, lawn mower fuel tank behind the seat in my pickup. It has come in handy a few times. I can rig it up fairly quickly. I also have an 3rd fuel tank hidden in my service bed that is not obvious to would be thieves.
The thieves also use Hefty trash bags to carry the fuel to a different location where they transfer it to their own fuel tanks via funnels. Keep in mind spillage is not an issue to them.
A bit off topic but FYI -Many years ago, while in high school , I worked summers at auto recycler- different from an auto dismantler. We had a $10million machine that used an 800hp electric motor to drive a huge drum with an array of pivoting “hammers” on its outer surface. The flattened car bodies, complete with engine and rear axle, were fed into the space between the rotating drum and the “anvil” where it would be shredded and then the rest of the machine was devoted to separating the various materials that make up the car. Occationally a car would come through with the empty gas tank still in it but full of vapor. When this would happen the explosion would give you shell shock if you were within a couple hundred feet of the machine. Everyone in the area had to stop work and take a 1/2 hr or more to recover to where you had your wits about you again. I’d like to see what OSHA would have to say about this today!!