Identify your use: baking (sponge, cake, sauces) vs. finishing (drizzle/soak), because alcohol-free swaps need extra fruit intensity.
Start with the listed ratio for your substitute, then adjust sweetness: if it’s sweeter than kirsch, reduce the amount (or reduce added sugar).
If using a juice/syrup/thinned jam, simmer or reduce 2–5 minutes until more concentrated so flavor lands like a liqueur.
Add your substitute at the stage the original kirsch would be added (mix-in for batter; last-minute for glazes/soaks).
Taste the final batter/sauce: brighten with a tiny squeeze of lemon or a pinch of salt if cherry reads flat.