In a medium saucepan, bring vinegar, brown sugar, and garlic to a low boil, whisking until brown sugar has completely dissolved. Boil, stirring often until liquid has reduced by half; liquid will be a syrup at this point. Lower heat to a simmer and whisk in the beef broth. Whisk in the tamarind paste. Stir in the ginger and simmer to let sauce reduce a little more. Pour sauce through a sieve into a serving bowl. Spoon over sliced pork tenderloin.