CoffeeBox draws attention to a commonly neglected source of coffee odor: residue inside lids, seals and other hard-to-reach parts of an insulated cup. The drink itself can also change during a long hold, so an unpleasant afternoon cup is not proof that the vessel is the only cause.
Begin with the manufacturer's cleaning instructions. Disassemble only approved parts, wash accessible food-contact surfaces with the recommended cleaner and tool, rinse thoroughly and let everything dry before reassembly. A cup body, painted exterior, silicone seal and lid mechanism may require different treatment. Avoid abrasive scrubbing that damages a coating or sealing surface.
For persistent stains or odors, use only a cleaning product and dilution approved for that vessel. Baking soda, oxygen-based products and acids are not interchangeable, and natural is not a safety or compatibility guarantee. Do not combine cleaners or seal a container while a cleaning reaction is producing gas. Inspect damaged seals and replace parts when instructed. A fixed soaking recipe cannot suit every insulated cup; correct disassembly and regular washing are more useful starting points than stronger improvised chemistry.
The conversation
A good question can make a better brew.