Dissolve 1 tablet of aspirin In about one and a half litre of water. Put your flowers in this water
These flowers have been fresh since 6 days already but were beginning to whither so I added aspirin.
You can also add a spoon of sugar and 3-4 drops of vodka. The vodka inhibits the growth of bacteria and the sugar provides nourishment.
Or you can add half a teaspoon of bleach in one litre of water and add a teaspoon of sugar.
Adding 1/4th of a cup of 7up or sprite to a lire of water also works well.
You can also stand about half a meter away and spray the undersides of the flowers with hair spray In addition to adding sugar and vinegar/bleach etc
Or add a teaspoon of vinegar and a spoon of sugar to a litre of water.
Basically we want to provide the nutrition the flower would have been provided had it not been cut.
In addition to these steps, it's important to change the water every 1-2 days and cut the bottom of the stems by a cm using a knife every 2-3 days.