Many fresh-cut flower bouquets come with a packet of floral preservatives, which you can add to the water in the vase. A floral preservative is typically made up of three main components: sugar, acid, and compounds. The sugar helps provide nutritional benefits to the flowers, while the acid lowers the water's pH. When the water doesn't have the right alkaline balance, minerals can build up and block the flow of nutrients through the flower stems. Compounds, the final ingredient in floral preservative, help prevent the stems from closing up. These additives help ensure that the flowers can continue to absorb the nutrients and water from the vase. If your flowers didn't come with a preservative packet, you can make your own by combining a few drops of bleach, vodka, gin, or another clear alcoholic liquid with clear soda and a crushed tablet of vitamin C.