Take six serving glasses and put them in refrigerator until chill.
Meanwhile, take a small saucepan and add one cup of water and 1/2 cup caster sugar to it. Place saucepan over low heat and stir until the sugar dissolves properly.
Now increase the heat to high for two minutes and do not stir the mixture at all. Keep it at high heat until the mixture become syrupy. Now cool it slowly and then put it in refrigerator or fridge until chill.
Take a large jug and place the sugar syrup, ice cubes, rosewater and chilled vanilla vodka to it. Now stir this drink to properly mix all the ingredients.
Add 2-tablespoon grenadine and 750ml chilled sparkling wine to the jug containing the mixture.
Take out the six serving glasses from refrigerator and equally distribute the drink among them. Your drinks are almost ready, top each of the glass with sweet peas and serve immediately.