You can certainly use balsamic vinegar in this honey ketchup recipe. Just take these things into consideration. Balsamic vinegar has a stronger flavor than white vinegar or apple cider or wine vinegars, so start with 1/4 cup first and add more if you want. It is also sweeter than other types of vinegar, so you might want to start with less honey and add more as needed. Finally, Balsamic vinegar is darker in color than other vinegars, so using it might result in a darker, more caramel-colored ketchup.