User experience problem: Sloshing half of the water you drink down your neck when using wide-mouthed Nalgene water bottles.
Solution: The easy sipper for the Nalgene bottles. Fill the bottle easily, put the sipper cap on, drink happily. Our lips and mouth only fit around so much of a bottle. This solution means that people who enjoy drinking from plastic bottles that they can wrap their lips around will have the same satisfaction from the more sustainable Nalgene bottles.