What if anything make a liquid a good candidate for a reduction?
The most important reason reductions exist, is because they intensify the flavour, so that's the first point you should pay attention to. Will the flavour accommodate the rest of the dish? White wine is often used in reductions for fish, red wine more often for meat. Everything that you think will fit, can be a good fit (other (stronger) liquors, vinegars (but don't use too much), ...). That's why you won't see liquids as coffee appearing in reduction recipes.

Wines and fruit juices give a fruity, softer taste, so they are a good fit with a lot of things. They also are largely water, so easy to combine with.

I must confess that I don't know how sugar content or acidity level will effect the reduction, but I do know that sugar and vinegar/lemon juice can be a component of reductions.