Not a syrup, a liquid. The original version used apple cider. I thought about trying something like pineapple juice or ginger beer.

Maple syrup is a definite possibility, because it starts as tree sap and is boiled down to syrup or even sugar. I've had maple caramels before. All I'd need to do is find a dark maple syrup that isn't too thick, which should be doable since many of the real ones are quite thin.