There is a good tool for drilling a nice clean hole through the centre of dildos and butt plugs. It is called a wad drill, and it is a hollow metal tube with one end sharpened to form a circular blade. As the blade end rotates, it cuts cleanly like a knife. The offcut material becomes a wad which slides up the centre of the drill as it advances. This procedure is used for drilling the ring-binder holes in publications.
It is very easy to make your own wad drill out of a stainless steel car radio antenna. Dismantle the antenna, and select a section of tube for your new wad drill. There will be a bevel at one end and a flange at the other, and these have to be ground away first so that both ends of the tube are now square and true.
You can do this by spinning the tube in your chuck (don't overtighten) while dressing each end with a flat file. Then, using the right-angle end of the file, held at 45 degrees to form a 'V', create the cutting blade by sharpening one end of the tube internally while it is spinning. And there you have it, your new wad drill.
Lube the drill inside and out with waterbase lube and water. Then, using slow speed (a drill press is best) drill down through the toy, starting at the tip. Apply only very gentle downward pressure as the drill advances. If it feels like it can't advance any further, withdraw the drill and poke out the centre wad. Apply more lube and resume drilling. Try and drill the whole length from one end only. This gives a smooth bore.
Safety Warning: Observe all safety procedures when using power tools. Please do not attempt this work if you are not familiar with the use of power tools.
For a hose attachment, you can use a small nozzle with the tip sliced off as an adaptor. Don't force the adaptor in too hard or it might split the toy.