When soil gets that dry it gets resistant to water, and will run right through the soil if you pour it in quickly, leaving dry pockets all over the place. You might have to go back and water them again, if most of the water ran right through the soil and out the bottom. I use 1 and 2 liter bottles to water mine, and I drilled tiny holes in one of the bottle caps and use that so i have a 'sprinkler type' water flow when i water. It spreads the water much more evenly, and eliminates that problem. When soil gets that dry I usually give them a light watering, then wait 15 minutes or so for the soil to moisten up, then go back and finish. That ensure that there aren't any dry pockets in the soil(a big no-no).