I don't know. Usually if I can't clean something because it's too narrow...or otherwise difficult to de-soil in any way whatsoever...I just throw it away and get a new one. Yeah right, you say? Well...yeah, you are right. Replace something every time it gets dirty? What am I made of, Smaug's treasure? Obviously I just give it to my mama and shower her with flattery about how she could win Olympic Gold in Cleaning Stuff until she offers to show me the best way to do it. At which point I always seem to feel a wave of diarrhea coming on and have to excuse myself. Anyway, maybe my mama would like one of these Cuisipro Magnetic Spot Scrubbers. They're pretty cheap, so I could get one and award it to her like a medal the next time my kraken flask needs a sudsing.
Glass erasers target awkward crevices and narrow spaces that are typically hard to clean. Wine decanters, pitchers, vases, baby bottles, bongs. Cuisipro's 2-piece solution pairs a knobby handle with a silicone scrubbing disc and magnet connectivity. Knobs set against the glass' external surface, lock to discs on the inside, and then glide over hard-to-reach areas for polishing. To finish, pull the knob away, let the disc drop, and dump it back out. Its soft rubber nubs keep glass safe from scratches and cracking.