Finally, a couple of additional laundry detergent bottles that screw together!
Here is what I think is a good way to insure that you do not waste liquid laundry detergent. To make this work, check the threads on the cap and note if they are on the inside or the outside of the cap. If the cap is threaded on the inside, then your next purchase of detergent should have a cap that is threaded on the outside. If your first bottle of detergent has a cap threaded on the outside make sure your next bottle of detergent has a cap threaded on the inside. So far, I’ve discovered that every time I have two bottles of laundry detergent with threaded caps inside and outside, I can screw the two bottles together exactly as if the bottles have their own caps in place.
When a bottle of detergent is low, I simply connect the almost-empty bottle to the new bottle and let it sit on top overnight, but sometimes the bottle on top won’t drain all of the detergent out as it sits this way. After the detergent bottles have been sitting this way for at least eight hours, tip the bottles left and right, forward and back, up to about forty-five degrees while they are still connected, to allow any remaining liquid in the top bottle to flow to the bottom bottle. Once this is done and you are sure all the detergent is out of the top bottle, it can be unscrewed and placed in your recycling container. Of course, if you are fussy about laundry detergent and always want the same brand for example, all of this cannot apply.