Add the entire can of cherries with the juice and the sugar to a small saucepan. Attach a candy thermometer if you have one. Bring the mixture to a boil over medium-high heat, stirring occasionally.
Reduce the heat and simmer with bubbles until the mixture becomes foamy. You want the temperature to get to 225° and you don't want the syrup to caramelize. The cherries start out a bright light red/orangy color but will slowly turn a dark red color and shrivel slightly. This is what you want! Whether you are using a thermometer or not, you are looking for a honey-like consistency and color change to know when the cherries are done. This took about 35 minutes for me.
Transfer the cherries and syrup into a sealable jar and allow them to cool before putting on the lid. You can refrigerate the cherries for up to a year (if they last that long!).
