What if we have been looking at it from a wrong perspective? What if the solution is not to change our ways, habits or even to change the design but the material itself? There are always people who will not recycle even when you offer money in return (In Croatia there is a pratice that you recieve around 10 cents per plastic bottle, those 10 cents are included in the price). We cannot force people to change their ways. However, what we can do is change the game completely.
I propose that we change the material, that the bottles and other plastic cups are made of a more friendly material such as industrial cannabis (the one that you do not smoke) or even algae. So why algae and industrial cannabis? I believe that those bottles would also end up in our oceans, but that would not be a problem. Algae is a plant in the bottom of the ocean and it is a food to herbivorous fishes (fishes that eat sea grass and algae). Those fish species are the first in the food sea food chain and we need them to have a balanced ecosystem. Phytoplanktons are the main food for other types of fishes humans eat. Anyway, bottles made of algae would dissolve in the sea and become the food for phytoplanktons. When phytoplanktons have more food, they reproduce easier and more -> they become food for other fishes -> which then humans eat basically closing the cycle. Furthermore, industrial cannabis is a plant from which we can produce up to 25 000 products and it is believed that it will substitute oil when we run out of it. It is organic and it could be a food for fishes.
For this solution we need to dry up the algae and grind them. Then we need to develop the packaging and make sure people use it and know about it.