Blue violets work best for this, but you may mix in a few yellow or white ones.
Remove and discard violet stems. Rinse violets gently with cool water in a colander, and remove any insects. Place 2 cups of water in a 1 1/2-quart saucepan. Add violets, cover, and simmer gently over medium-low heat for about 10 minutes. Remove from heat; let steep, covered, for 20 minutes. Strain liquid through damp cheesecloth or a coffee filter; the liquid will be green.
Measure 1 cup of liquid. Pour into a small saucepan; add the sugar. Bring to a simmer over medium heat; reduce heat to medium-low and simmer for 5 minutes, stirring to dissolve sugar. Let cool for 5 minutes. Slowly add just enough lemon juice for the liquid to turn purple; the acid in the lemon juice is balancing the pH of the liquid. Don't add all the lemon juice or the liquid may turn red.
To make one serving of Wild Violet Sparkling Water, add 1 tablespoon of Violet Syrup to sparkling spring water.