My DD was admitted to hospital with tonsilitis & glandular fever & the main reason we were in there so long is because she refused her meds. They had to put a nasal gastric tube down. She was really dehydrated as well.
Have you tried it in a milk shake? Thats how I got them into DD after hossy. Warm milo's were good too. But she was on abs, I think they are a bit easier to hide.
I find white/pink creamy type medicines are easier. The clear/red medicines are really hard to hide.

Bribery is good too. I know it shouldn't be used, but a drink of lemonade, or a choccy frog after might help?

Goodluck My sister just got over it. The cough will last a bit afterwards if she has it the same as my sister & mum.