Well, sukiyaki sauce is not all that advanced really :\

You can get away with using only sake by adding more sugar, and you can get away with using only mirin by using more soy.

I've heard people have used chinese rice wine as a common substitute for the sake/mirin, so I guess gin or sherry might work if you don't use a lot.

You're also supposed to be able to use pinapple juice instead of mirin if you're really desperate, but I would just make something else :P