I put a hose on a nipple just below my throttle body. The hose had a tiny restrictor in it (the hole was about the diameter of a thumb tack) and I just put the other end of the hose into the jug of water.
Letting it idle caused water to pool up in the intake, and when I revved it a significant amount got sucked in at one time. Not a good thing, because my car was tilted at an angle, which darned near made one of the cylinders get too full. There's a lot of vacuum at idle, which makes it suck water FAST, even with such a tiny hole for the water to go through. You're better off running the engine at 1500-2000 RPM, which will help to prevent stalling, and will also lower the amount of vacuum trying to suck the water in.
I've used both cold and hot water, and the hot water gave vastly better results.
After you've sucked about half a gallon of water in, take it out and flog the heck out of it once it stops sputtering. That will help loosen up and burn off the carbon. Come home, repeat.
If you have something with the ability to create a steady mist of hot water that you can put into your intake before the throttle body, that might give better results by distributing the water evenly to all cylinders. It will also cut the chances of hydrolocking a cylinder.
Even with my tiny restrictor in the hose it still only took about 10-15 minutes combined to suck up 2 gallons of water.