After fixing my buckles (https://www.myminifactory.com/fr/object/42284), I thought it would be a good idea to create this adaptator, but for the coca-cola bottles. The design is similar, but you will need the other accessories (that you can find on the website of decathlon «Water bladder» ). The tube (8mm diameter) can be found in most websites.

For this design, you have to print it with the thread facing up (to avoid support inside).