Add 4 or 5 drop of bitters to the glass, twist to ensure the glass is covered, add 4-5 ice cubes, vodka, and either juice of 1 lime, or 1 measure of lime cordial, top up with soda. Add lime wedge to drink.
A long cool drink that hits the spot, you can subsitute lemonade for soda if you prefer a sweeter drink, but soda is more refreshing.