Cherries out of season - what can I use?

CanuckFoodie...
Depends on where you are
There seem to be smallish producers out west (e.g., Vancouver, Saskatchewan) who freeze their sour cherries.
I've seen far fewer frozen cherries in Ontario.
Other options include dried sour cherries and, yes, the bottled ones.
If you use the dried ones, I suggest you reduce the volume or expect a more intense flavor than from the fresh.
If you use the bottled ones, reduce or eliminate the sugar in the recipe.
Bottled sour cherries DO have flavor and have worked in desserts like Black Forest Cake.

I would recommend frozen sour or tart cherries over the jarred variety, which I think would work best because canning or processing in jars requires the addition of a liquid which might wash out some of their flavor and juice. You can also find concentrated sour cherry juice in some grocery stores, as well as online- and I'd be tempted to use some of that as well. You could add that in with the wine and sugar, and beef up the cherry flavor. Just be careful when you get your cherries not to get the sweet sort by accident.