To carry our water we each have a Sigg bottle and a Platypus bottle as back up when we expect a long, hot day with limited replenishment opportunities. I also use a pilots' flask as EDC around town and as an occasional spirit flask on trek. When not in use, the bottles are kept empty and unstoppered. Every once in a while, I clean our bottles by scalding them out then steeping them, and their stoppers, in a mix of lemon juice and bicarbonate of soda before giving them a final thorough rinse in water from a trusted source, such as a tap. Despite this treatment, my wife insists that she can detect a strange taste in her Sigg and especially in her Platypus bottles. If pushed, I too can detect a slight taint, but I'm not so fussy and, unlike her, I am not susceptible to digestive problems. I notice a strong taste of brandy lingering after a couple of refills of my pilot's flask but treat this as a bonus and am in no hurry to remedy this. Has anyone else encountered a similar problem and if so, what did you do about it?