What? You need ENERGY to stay alive, and to be able to do anything, e.g. fight off infection.
If you go on some crazy fruitarian diet you're only going to make yourself ill(er) because you won't be taking in enough calories, which you get from carbohydrates and fats. You might be getting some sugars from the fruit, but probably not enough. And if you're repairing damaged tissue you'll need protein too, of which animal products are a much better source than plant ones.
listen to this at your own peril. most of it is very, very wrong.
energy does not come from protein and especially not cooked meat. this is absolutely false. a world wide common misconception.
burnt animal protein toxifies your system, slow down your system, weighs down your body by requiring lots more energy to digest, and leaves harmful chemicals behind.
the human body needs very little protein to stay strong and healthy. if one was to eat meat, a piece of it the size of your thumb contains enough protein for a week.
i know this from trusted sources of knowledge as well as personal experience -- after 40 days of NOTHING BUT vegetable juice and herbal supplements, having not had a single gram of animal protein, i had MUCH MORE PHYSICAL ENERGY than when I am eating "normally".
oh and i absolutely discourage from normal over the counter cold medicine. that stuff predominantly fights short term symptoms and prolongs the actual illness.
and booze weakens the immune system even more than normal food. sure it can kill germs but unless the germs are in your stomach, and in the case of a cold / flu it isn't, alcohol doesn't do shit other than make you weaker.