Step 2: Put it all together
Drill a hole in the bottle cap, I used the awl on my Swiss Army Knife (Swiss national anthem playing in background), so that I wouldn't get it too large.
Shove the tube through the hole, it should be tight. You can seall it with hot glue, but I didn't. I figured it would allow a little air to back flow into the bottle as I drink. It turns out that almost no air leaks through, but it works well enough without the hot glue. Glue would totally seal it, however.