Place the rhubarb, ginger, water, and sugar into a small saucepan over medium heat. Allow it to simmer until the sugar has completely dissolved and the rhubarb has softened and begun to break down.
Add the rhubarb simple syrup to a food processor or blender along with a strawberry if adding. Blend until smooth.
Pour the mixture into a fine mesh strainer over a bowl or glass. Use a spatula to force it through, removing any of the larger more fibrous pieces.
Keep stored in an airtight container in the refrigerator until ready to use.
Rhubarb Ginger Gin and Tonic
Pour the rhubarb simple syrup into the bottom of your cocktail glass.