Whether milk, protein powder or added ingredients have given your gym shaker a funky smell, there’s an insanely simple way to take care of it. You have to think that if you have a manual shaker, the metal mixer in the middle can scratch up the inside of the shaker. If you stir it with a metal spoon or fork, you could scratch up the inside. This creates micro divots that can hold onto trace elements of bacteria, protein powder and milk. Sounds gross, but this is how you fix it.\r