glass is theoretically more sustainable, while its production does not involve the same kind of problems as plastic it is a lot more energy intensive so without proper energy infrastructure it is trading plastic pollution for carbon emissions, also heavier contributing to transport costs. With proper infrastructure for reusing the bottles the energy impact of production can be mitigated significantly. and even without proper reusage infrastructure the options for the glass is 1. resmelted into new glass 2. landfill->glass shards quickly become essentially just sand 3. environment where it also becomes sand

so while even without proper infrastructure the pollutans are essentially just emissions if properly treated just co2 (though modern kilns can be electric arc reducing emissions just to that of the country's electricity infrastructure) and gravel. In contrast plastic has lower production emissions but the waste in environment is to put it lightly quite a bit more harmful than gravel and the effects are still not fully understood especially ones of microplastics