Combine sugar and the water in small pan; simmer
over medium heat, stirring, until sugar dissolves. Transfer
syrup to large bowl to cool completely.
Puree strawberries and lychees in a food processor
or blender until smooth. Strain through a fine strainer.
Add puree and lemon juice to cooled syrup. Transfer
to a 13-by-9-inch glass dish. Freeze, uncovered, raking
with a fork every 30 minutes to keep it from becoming
too solid, 2 1/2 to 3 hours. Serve immediately.