A cup of hot calamansi without sugar is good for flu.
Also drink lots of water and eat plenty of juicy fruits like lemon and oranges.
That can help minimize flu if not totally prevent it.
Ahhhhh, the goodness of Vitamin C and citric acid. The other part to this is to constantly sip on strong hot tea (preferably peppermint). A sip every 15-20 minutes does the trick.