Yep it's difficult. Usually when I'd get a cold(let alone a flu) I would drink lots of hot tea and that sort of thing. What I have done really is make any fluids I do take hot ones (I know tha seems a bit silly but just something I'd do - plus I find hot tea helps when I feel horrible) and I take some vitamin C (but I also know the chewable kind has sodium in it so I don't take too much) and well I just endure it.
I also have the flu shot every year (and of course I just had the swine flu shot last week)
Sorry can't be of much more help with that one. It really is annoying because hot tea and hot soup used to be my staple when I had a cold or flu... now... not so much