Web search finds info. I looked recently because of similar issue. Most promising approach seems to be drill a hole in the battery, drive in a sheet metal screw, and pull, lubing with wd40 if you can get it around the battery casing. Do this outside with eye protection and gloves as the battery can spew crap when you drill it. The batteries are called alkaleaks for a reason.
Other people suggested stuff like vinegar and baking soda, which sounded useless. If you use a vise, obvs wrap the light first. Let us know how it goes.
I think flashlight enthusiasts are far less likely to use alkaline batteries than the average person, but most of us have encountered the question in a forum once or twice.
Solrize gave the standard answer. Water should be your first try for cleanup after you get the batteries out, but if you have stubborn residue, vinegar will react with the alkaline electrolyte.
I’m saying if the light is powder coated finish acetone will take that finish off.
I’m which you may not want to try it. Someone correct me if I’m wrong but If it’s titanium, copper or brass Id give it a go.