Sickness and Diarrhoea
The reason why you get sickness and diarrhoea is that your body is trying to get rid of the bug which is making it feel unwell. So, although it is not very pleasant, it usually serves a purpose. The best thing is to let the illness run its course for a few days whilst your body gets rid of the bug.
You can help yourself by taking plenty of liquids and limiting the food you eat. (Most of us won't come to any harm by not eating for a couple of days). Often the best fluid is clear lemonade, which you flatten by leaving the lid off the bottle or putting a spoonful of sugar in a glass of water and sipping it.