PVC window frames - where to fix a curtain?

I need to put up extra curtains to keep out sunlight (and similarly in winter when extremely cold). What kind of fitting can I use, and where and how to I make holes in PVC frames? Sticky-back hooks don’t hold up. On a small window I have used the light weight spring loaded rod inside the reveal, but that’s no good for a door that opens inwards as pictured. Suggestions please!