There are a few things you can do to clean a hydroflask:

  1. Fill the flasks with water and bring them to a boil. Remove the top from each flask and place them in the boiling water. Let them sit for about 10 minutes, or until they start to clear.
  2. Pour out the water and dry the flask using a cloth or paper towel.
  3. Put the flask back on the shelf and enjoy your delicious drink!