Some use windshield washer tank + pump and oil burner 'injector' (those that are warming houses; burning oil, heating water) Some alcohol in mix is good for cold areas.
Simpler method is to spray water to radiator or intercooler. With intercooler and turbo motor it is not the most clever idea to put water before intercooler, but I have seen that done too, now how do you drain intercooler of water then?
Old times when engines got carbon buildup easily, water was used to clear the engine, 3000rpm or so and then water to intake, not so much that engine stalls, but enough to effect running and that did bring back missing ponies, but some managed to cause hydro lock destroying perfectly good engines, so too much is too much, too little did not clean engine. I remember that glass or bottle was 'injector' so it is quite hard to cause serious problems with injector put to intake manifold.
If my intake would be any way sensible, I would do water injection, but as my intake is behind the motor, below intercooler, it is real pain to remove it, I think removal of cylinder head was needed to be able remove intake manifold, so I don't think that I will do it.