An idea I used many years ago when I made a really bad batch of Apple wine (flavourless and thin) was to take the liquid and put a couple of litres in the freezer, I use an old Lemonade bottle. Allow it to freeze and then take it out, leave for about 1/2 an hour and start to pour off the melted liquid.
The first thing you will notice is that the liquid darkens, this is a sign of things to come.
Once you have got about a litre of liquid back, stop the process. You can throw the rest away.
What we have here is a little basic physics and chemistry. Alcohol melts at a lower temperature than water, so the first thing to come out of the frozen wine is the alcohol. Simple maths and you should realise the water content is now lower and the alcohol is approximately 100% stronger. So a 8% wine is now 16% (we hope). Also the colour comes with the alcohol so we should have a deeper and richer.
Warnings, it may still taste bad, or it could just save a bad batch. If you start with a dark colour, it will get darker, so if you do a dark beer, you may get an almost black beer back.