Customers say these tablets are easy to use and effectively remove stubborn coffee and tea stains from water bottles, thermoses, and mugs. Many reviews highlight how quickly the product works, often requiring just 15-30 minutes with hot water to restore containers to like-new condition. Users appreciate that the tablets leave no chemical aftertaste and work well on various materials including stainless steel and insulated bottles. Common feedback mentions the tablets are convenient for regular maintenance and work better than alternative cleaning methods. A few users note that heavily stained items may require multiple tablets or longer soaking, and occasionally a brush helps with stubborn residue.