Rainiers are stunning in cocktails in place of fluorescent maraschinos (and are great on ice cream too). They'll start to darken after a month, but will taste even better.
Put cherries and cinnamon stick into a 1-qt. sealable glass container, such as a mason jar.
Bring sugar, brandy, and 1 cup water to a boil in a small saucepan and boil until sugar has dissolved.
Pour hot liquid over cherries and let cool to room temperature, about 2 hours.
Seal jar and chill until cherries have shrunk and absorbed liquid and are flavorful, at least 1 month and up to 4 months.