It’s pure plastic waste at that point. No one is going to be making plastic bottles for the purpose of dissembling them into hydrogen fuel anymore than they are currently making plastic bottles for the purpose of sending to waste-to-energy plants (incinerators).
It’s not just plastic. It’s plants too; ideally agricultural and industrial byproducts.

Solar reforming has emerged as a class of sunlight-driven technologies capable of converting waste-derived substrates into fuels and chemicals. By utilizing substrates such as glucose or ethylene glycol (EG), derived from lignocellulosic biomass or polyethylene terephthalate (PET), as electron donors, solar reforming enables a more energetically favorable oxidation pathway compared with water oxidation.

source: the paper linked in the article (emphasis mine)