Nothing is more inconvenient than discovering that you're out of a pantry staple right in the middle of baking. Honey, however, is an ingredient that's fairly easy to substitute.
A 1/4 cup of granulated sugar dissolved in 1/3 cup of water is a fairly successful dupe for one cup of honey. Corn syrup or treacle can sub in for honey at a 1:1 ratio.
As you might imagine, these substitutes don't behave exactly like honey. Your baked goods may take longer to cook, since honey caramelizes faster than other types of sugars.
Your desserts may also be lighter in color. As for flavor, it's impossible to replicate honey's exact nuances, but treacle tastes more similar to honey than sugar or corn syrup.
You'll want to use treacle as a replacement in recipes where honey plays a bigger role and isn't disguised as much, like in marinades, dressings, or glazes.