Dear Mrs Jayshree
Welcome to HCM
Greetings of the day
It is totally inadvisable to give alcohol in any form for treatment of cough
. Alcohol acts as sedation and induces sleep and indirectly suppresses cough which could be counter productive in children which could lead to retaining of secretions and predispose to severe infection. Just remember cough is a protective reflex, so treat the cause of cough and it will be fine.
Time for you to visit a qualified personal like Pediatrician
to seek professional advise instead of experimenting.