I agree with syringe idea and you shoot it as far back in their mouth as possible.

I haven’t given medicine to kids for years, but I have a difficult dog. I use a syringe (no needle) and poke it as far back as possible and squirt. No issue to spitting it out

Medicine Dummy
Or I used to blow in my daughters Mouth whilst she screamed Blue Murder, and it made her swallow when I blew, Not the best thing but it worked.

I was told by a midwife to squirt medication at the side of the mouth (or cheek pocket ) as they are less likely to spit it out

You need to be so patient, it can get frustrating.

For a small child you need to put liquid medicine in a small disposable syringe first. The trick is to hold either side of the chin with your fingers/thumb firmly but gently( so jaw won’t move too much and the child can’t pull away). Place syringe to inside mouth but to the cheek side not middle of mouth and half-way or so to back of cheek and administer medicine (this stops the the child gagging and spitting the medicine back out. Gently push chin up to close mouth if required to keep medicine in!

Yes chewable tablets is an idea and otherwise you can always give panadol suppositories. Different brands have different tastes, so also try maybe some different brands ?

My son won’t take panadol either until I found children panadol in a chewable tablet and the first time I gave it to him he asked for more Mabye give them a try