I thought I had found the perfect hole-making tool by using my Dremel. That stood until I was looking for something quiet and sharp. I picked up a Stanley Scratch Awl (from my grandmother's sewing box) and I am amazed. The awl pokes through milk jugs like a hot knife through butter, it poked through hard juice bottles (think the kind grape juice comes in) with some pressure, and it pokes through 2 liter soda-type bottles. The latter collapses a bit with pressure but can be popped back into shape.
I love this awl. No heat needed, no power, and now little shaved bits off hot plastic hitting me from the drill bit! My awl is likely 60 years old, but Stanley still makes them and I think they can be had for about $6.
On another forum someone suggested putting containers with drainage holes in a shallow cardboard box. The box will not hold the drained water. Another advantage the box will keep the containers corralled so they won't blow over. If the containers don't fit the box fairly snuggly stuff some rolls of newspaper between the containers.
I haven't been heating the awl point at all. It just loves poking through milk jugs without heat. It works for the others too, just with more pressure. It's good stress relief! It does look a bit like a short ice-pick. I found two of these awls, one in my grandmother's sewing kit and another I had bought likely in the late 1980's or early 1990's when I used to do some leather work. I did a web search and they are still made today. I have the Stanly model 69-122. Our local Ace hardware sells another version by some other company. To be honest I don't know what they are intended to be used for... but they work great for poking holes in leather and now I know in plastic as well!
I like coraling containers in anything that holds some water but *leaks slowly* (like most cardboard boxes, or like a plastic 1020 tray that's developed a couple of small holes or cracks). That way, I can fill up the box/tray with water to bottom-water my WS containers... the potting mix soaks up as much as it can, and after a few minutes the water has drained away.