Combine the Rhubarb Syrup, tequila, lime juice, triple sec, orange juice, mint leaves and some crushed ice in a shaker. Combine in batches, if necessary.
Place the strawberries in the bottom of 4 margarita glasses. Strain the margaritas over the strawberries.
Combine 1 1/2 cups water and the sugar in a medium saucepan over high heat. Cook until the sugar is dissolved. Add the rhubarb and cook until slightly softened, about 5 minutes. Remove the saucepan from the heat and steep for 1 hour. Drain the liquid into a small saucepan and cook over high heat until slightly reduced and thickened, about 5 minutes. Transfer the syrup to a bowl. Cover and chill in the refrigerator for about 1 hour.