Stir together water and sugar in a mason jar or glass bowl then microwave for 1-1/2 minutes. Carefully remove from microwave then stir until all the sugar has dissolved - you now have simple syrup. Refrigerate until completely cool - simple syrup can be made several days ahead of time.
Combine lemon juice and strawberries in a blender then blend until very smooth. Stir in coconut water then simple syrup to taste (I use 1/4 cup + 2 Tablespoons of simple syrup - amount used will depend on your tastes and how sweet your strawberries are.) Refrigerate lemonade until ready to serve then pour into cups with ice and top with sparking water (optional) just before serving.
Notes
Tip to get more juice out of lemons: microwave lemons for 20-30 seconds then firmly roll against a cutting board before slicing lengthwise and squeezing.
Add a splash of vodka or champagne for a little fun and/or turn leftovers into popsicles!