1
Pour a cup of water in the liquid measuring cup. Add one cup of distilled vinegar.
2
Mix the water and vinegar together in the measuring cup with a spoon. Mix until combined the two liquids thoroughly.
3
Water to a boil and fill the flask with boiling water. Pour it out, and repeat again. Make sure to burn in the process, and hold the metal flask with a towel or potholder if necessary to protect yourself.
4
Fill the flask approximately half full with water and vinegar solution. Close the top and shake vigorously for about 20 seconds.
5
Pour the solution. Repeat Step 3 and Step 4, or rinse with boiling water, then the vinegar solution. After repeating these steps to fill the flask with boiling water or even clear out remaining vinegar into the hip flask. Turn your head on a paper towel to dry. The water comes out and be absorbed by the paper towel.
