This is useful for when the protein powder sticks to the walls of the shaker cup after you’ve had your drink.
1. Rinse well with warm water.
2. Fill up a third of the cup with warm water from the tap
3. Add some white vinegar. One or two tablespoons depending on the situation.
4. Close the lid and shake well for a few minutes.
5. Dump the mixture and rinse well with cold water.
6. Clean the screw part with a toothbrush if necessary.
If the result was unsatisfactory, then consider adding hotter water, or more vinegar the next time you clean the shaker.