Things that should have fill levels in their look or scrutinize.
Perfumes and Colognes.
Bars and Kitchenette's.
One other thing came up in head that I haven't checked in a long while so I could be wrong about it not showing a fill level.
My idea is to add a relative fill level to the look of these or to their scrutinize possibly to the use screen for the bar or kitchenette if it's something you want to obfuscate from the general public.