Place the cherries in a medium size saucepan and add about a cup of water (or more to make sure the cherries are submerged in the water)
Bring to the boil and then let simmer for 5-10 minutes or until the cherries soften.
Add the sugar and carry on heating on a very low heat, allowing the sugar to dissolve (but not boiling the mixture at this stage). This might take about 3-5 minutes.
If the cherries are soft and falling appart themselves, just pour the mixture through a fine sieve. Alternatively you can also whisk the cherry mixture in a blender or a food processor.
Making sure that you get as much flavour as possible, push the cherries into the sieve to get as much of the liquid out as possible.
Depending on the sourness of the cherries, add half of the lemon juice cup and a cup of water. Taste and add more lemon juice and more water depending on the taste.
Pour into glasses and add ice cubes and garnishes to serve.