The recipes for fruitcake that I've looked at say to soak the dried fruit in brandy, rum, etc., i.e., something with a high alcohol content. I've been using liqueur which works well.
I was wondering if using a sweet wine would work; has anyone tried this?
A good quality ($20 or so) sweet Port, Madeira, or Sherry could be lovely, and add a delicious flavor note of its own. Make sure it's something that tastes good by itself, with a flavor that appeals to you, complimenting a piece of cake.
Note that these are so-called "fortified wines" — they are distilled to a higher alcohol content. Historically, this was done to achieve a long shelf-life without preservatives, so they're more like spirits. Unlike regular "corked" wines, an opened bottle of fortified wine can last a long time, so the cork is made as a stopper that can be easily resealed.
I don't think you'd get good results with a moscato or such. I also wouldn't skimp and buy a cheap (e.g.: Taylor) bottle of Port — that would be like using cheap, imitation vanilla extract! Spending $30 to get a high-quality flavor that you enjoy, is money well spent.
This kind of wine typically comes in both sweet and dry variants. If you're making an entrée sauce, you probably want a dry wine. For fruitcake, be sure to select a sweet variety. Sometimes, they're not specifically labeled "dry" or "sweet", so you need to read how it's described the label, or ask your vintner for a recommendation.
You can, but it will have a very different effect to your fruitcake. The booziness of liquor is what makes the fruitcake taste the way it does.
The fruitcake will probably still taste great, but it won't be what people expect from a fruitcake, which is the boozy mouth and nose feel of the cake.
