Add rhubarb, strawberries, water, orange juice from 1 large orange and orange zest to cooking pot.  Bring to boil. Reduce heat to simmer and cover pot. Simmer for 1/2 hour, stirring occasionally.

Strain juice into clean pot. Discard the fruit pulp or use for smoothies or toppings for ice-cream and oatmeal. 

Add sugar to your juice and bring to a low boil until syrup has reduced and thickened. About 45 minutes. Stir frequently. I prefer a thick, concentrated syrup and therefore will boil until it's reduced about half. Remove syrup from heat and add lemon juice. Cool.

After syrup has cooled, store in fridge. I freeze some syrup for future use by storing in 1 cup freezer safe containers.  

To make your sodas, simply had 1/4 cup or more to a tall glass and fill the remainder of your glass with your favorite sparkling water, club soda or seltzer water. For a lighter tasting soda, add less syrup. For a heavy fruit flavored soda, add more syrup. Sometimes I experiment with flavored sparkling water and the results are always fun and tasty.