Paracetamol, rest and stay hydrated.
I don’t buy into all this ‘manflu’ bollocks, it’s just sexist BS, but it seems to drive some to pretend they’re not ill, or think they can beat an infection through willpower.
Worse still you get the type who’ll show up day after day for a week in work, do next to nothing because their brain isn’t working properly, make everyone else sick – THEN take the day off they needed in the first place. Just sit on your arse and watch TV for a day and you’ll be better sooner and you won’t bring the whole office/workshop/site/mine/sweatshop down with you.