A bottle or jug which will hold 1 litre of liquid and fit in the fridge (or you can chill it with ice)
Water
Juice from 4 lemons
100g caster sugar
Method
Boil some water and add a little to the caster sugar (enough to cover and dissolve the sugar, around 200ml will do)
Stir the boiling water and sugar until all the sugar has dissolved
Pour the sugar water into your bottle or jug
Pour the lemon juice into the bottle/jug
Top the bottle up with cold water to make up to one litre then mix (or gently shake if its in a bottle)
Chill in the fridge until you are ready to drink it. Best served with ice. (I have mine in a reusable Starbucks plastic frapachinno beaker filled with ice).
Best used within 2 days (ours lasted all of a few hours and then we had to make more! Yummy)