In a small pot, bring rhubarb, sugar, and water to a boil over medium heat. Cook, stirring occasionally, for 5 minutes or until rhubarb is soft and cooked through.
Transfer to a jar, cover, and allow to rest at room temperature for 24 hours.
After 24 hours, strain using a fine sieve with a coffee filter or 3-4 layers of cheesecloth.
Store in refrigerator for a few weeks.
Notes
*For strawberry rhubarb liqueur, replace approximately half of the rhubarb with strawberries.**The fruit will give lovely flavor to the vodka, so no need to use expensive vodka.