One of the things about making your own tonic syrup is that you really don't use much for each drink, and the potential uses are admittedly more limited than a straightforward flavored syrup. So what do you do with a whole ton of tonic syrup, with nary a drop of gin, aquavit, etc. in sight? You do insane things, that's what.
Before you go judging this recipe on the merits of its appearance, try one. This is bizarre, unexpected synergy in a glass.
2 oz medium-dry sherry (rainwater madiera might work too)
1 oz white rum (Plantation 3 Star; I wouldn't use anything too dry, i.e. Bacardi)
1/3 oz spiced tonic syrup (up to 1/2 oz depending on your batch)
Combine over ice and stir, then top with 1-2 oz soda water to taste.
I know, I know - that looks like a fucking train wreck. It was only through the miracle of multiple previous drinks that this combination even occurred to me, and then just as a sort of befuddled curiosity. I've never been more pleased to be proven wrong.