I had to give eye drops to a cat that does not enjoy being forced into physical contact at all. After two days of my partner and I pinning her down and getting most of the stuff over her face instead of in her eye, I found this method described online:
Get a hoodie or sweater or something with elasticated wrists.
Shove cat in hoodie towards one of the sleeves.
Pull sleeve down over the cat so their face pokes out of the end.
Cat can now not move their legs, and if the wristband is narrow enough, shouldn't be able to hook a paw through a drag themselves out.
Congratulations, you have a cat sausage. Position wherever feels most comfortable (I had mine on her back for the eye drops) and do what you need to do.
You can do this solo and don't need to spare a hand to keep a blanket wrapped round the cat while you try and administer medicine, and it's over pretty quickly so minimises stress to the cat. Would probably work for oral administration too.
When you're done you can either pull the sleeve so the cat comes out backwards, or stretch the wristband/cuff bit so they can wriggle out forwards.