Cook maple syrup in a saucepan over medium-low heat 1 to 2 minutes. (Don't let syrup get too hot or cranberries will pop.) Remove from heat; stir in cranberries. Cover and chill 8 to 12 hours. Place sugar in a large bowl or baking dish. Drain cranberries in a colander (about 15 minutes). Add 4 to 5 cranberries at a time to sugar; gently toss to coat. Repeat with remaining cranberries. Place cranberries in a single layer on a parchment paper-lined baking sheet; let stand until completely dry.