Maybe it will be useful to others. My father has P.Cancer and he started hiccup constantly. We tried a old Greek practice and it had results.
You boil in low fire 3 tbsp dried clove powder, 2 tbsp extra virgin olive oil and 100 ml of water for 20 minutes. Then you drain the mix (through a coffe filter for example) and you take 1 tbsp of this every 2 hours more or less.
It has work with very good results so far.