How do you ensure that the collected drinks containers are actually recycled into new bottles?

The SUP (Single Use Plastic) Directive of the EU (2019/904) stipulates that from 2025, producers must ensure that each PET bottle contains 25% recycled material. In other words, producers must have access to recycled material in order to fulfil this stipulation.
The stipulation regarding the proportion of recycled material will increase continuously over the coming years. This proportion must amount to 30% by 2029.