Hi folks. I thought I might bring you up to date on my efforts to repurpose a cheap screwdriver motor. I have to say that it looks like a complete success. See the attached picture below. I have only tested it with 1kg and 2kg weights since I don't have any larger water bottles, but the motor easily handles that load and supports it without power at any intermediate height (in the photo the bottle is suspended about 600mm off the ground). I have no doubt that the motor would be happy with 3kg (my original design wish), though the same might not be said of my temporary mount - it isn't fixed down so needs a heavy counterweight to avoid any risk of tipping.
Oh yeah, tips for others about the importance of the spindle! I made my spool on a small metal lathe I have. You want one which has as narrow a diameter as possible, consistent with the load, as that maximizes motor torque. The bevelled sides resist the potential of the thread jumping off the end. I also found it worked much better with that blue guide beneath the spool, which steers the thread back towards the center, otherwise it'll want to keep winding in one direction. It would actually work better if the guide was a small hole instead of a V, I'll do that next time. Oh, and the "thread" is actually 100lb (45kg) braided fishing line, only 0.25mm thick - you want narrow thread to keep the spindle diameter down and torque up.