This is lovely when you are not very well. Actually, it's lovely even when you are well, but I do try not to have drinks with calories in them (other than alcohol and maybe fruit juice) when I am well!
1/2 cup pearl barley
1 litre water
Generous pinch salt
3 large unwaxed lemons
100 g sugar
Another litre or so of water or ice!
Put the barley, water and salt into a saucepan, bring to the boil and simmer for about 40 minutes, until the barley is cooked. Drain, and put the barley to one side to use in something else.
Using a potato peeler or lemon zester, peel the lemons, being careful not to get any of the pith. Put the peel and the sugar into a plastic jug, then bring the barley water back to the boil and pour over it. Stir to dissolve the sugar, and leave to steep for about 5 minutes. Meanwhile, squeeze the lemons.
Strain the barley water into the lemon juice, then top up with ice-cold water (or ice) to make about 1.5-2 litres. Serve as cold as you can (stir before serving if it's sat for a bit).