“Malt is tricky, and sometimes gross. In my experience, the best you can hope for is vegemite, marmite, or some other yeast extract. If you have chocolate malt balls or some other malt based candy, those can be ground up and used as well”. Andrew Thaler
These “malt” sources don’t have active amylase enzymes – they at best would be an additional source of fermentable sugars and amino acids that would help yeast activity. They would not degrade the starch in the the processed cereals. The repeated extraction through the coffee maker would extract all [most of] the available simple fermentable sugars, a fair amount given that many of these cereals were probably steamed during processing with some thermal starch degradation. The dried fruits would be great sources of fermentable sugars, not just a flavor modifiers.
So what could he do to make this process somewhat more efficient?
If the ship’s bakery had malted barley flour – with active amylases that’d be best – that’s probably unlikely, the ship’s chef/baker would probably use a bread flour that would possibly have malted barley flour added at the mill. This is usually a vanishingly small amount of malt flour, because in breadmaking you only want extremely limited starch digestion for just enough fermentable sugars for the yeast. Adding some of the bread flour (check the label for the malted barley flour – e.g General Mills’ Better for Bread has it – just an example, not an endorsement) and maybe having longer period of digestion for the mash. This would mean that the coffee maker hotplate might be a bit warm and thermally kill the amylases so if you could keep the mash at about 60 deg C** this would maximize the beta-amylase activity and create a wort with the maximum fermentables possible with this crude, but brave, method.
**This should be possible on any modestly sized oceanographic research vessel.