Ok this picture is from a great website that teaches you to hack all kinds of thing to make better uses put of them...check em out here! http://www.instructables.com/id/How-to-remove-the-cap-on-a-Swiffer-Wet-Jet-cleaner/
Written By: cpd_trigger
step 1: Removing The Cap
In a small pot, bring just enough water to cover the cap to a boil. Once you've brought it to a boil, place the bottle, cap first, into the water. After about a minute and a half, remove the bottle from the water, and give the cap a good, hard twist. It should pop right off as the boiling water will have softened the plastic cap.
step 2: Making the Cap PERMANENTLY Removeable.
When you get the cap off, you'll see that it has a number of prongs which cause it to catch on the bottle. With a pair of finger nail clippers, remove these prongs. You could also use an exacto knife, or even a razor blade, but I had a pair of clippers sitting around when I thought about doing this.
step 3: Refill the Bottle
Now you're ready to refill the bottle with your cleaner of choice. Vinegar and Water, Pine-sol, or anything else you may want to clean your floors with. Place the cap back on the bottle firmly and you're good to go. Hope this saves you some cash in the long run.
Another tip that was given is as follows
1. Get a pair of channel-lock pliers.
2. Adjust the pliers to the width of the bottle cap so that you won't crush it when you apply pressure.
3. Twist off the cap.
4. Fill the bottle with floor cleaner.
5. Replace the cap.
The cap will screw back on without a problem and you won't need the pliers to remove it the next time.