Vodka

Vodka is an European clear distilled alcoholic drink that has been one of the most popular drinks across the world .

You'll find it to be the most popular spirit in drink making because of it's neutral taste and absence of flavour and colour.

Vodka often replaces Gin in many traditional cocktails

Vodka is known to be good for the heart, and if consumed in moderation, can prove to be good for cardiovascular health

Note that these days there are flavoured Vodka available in the market too, and some cocktails do make use of them.

Lime Juice

Lime Juice being rich in Vitamin C is an excellent remedy for sore throat and aids in digestion and controls blood sugar, and also promoted weight loss. It is used for various culinary and non-culinary purposes all over the world. Lime juice is known to reduce or even reverse the effects of excessive alcohol consumption and intoxication.
The difference between Lime Juice and Lemon Juice is that although the sweet and sour Lemon and the bitter and sour Lime are two different fruits, they have similar properties and tastes similar too, the Lime, unlike the sweet and large Lemon, is used raw and is usually plucked green and has more bitterness and sourness in it's taste, and is grown better in tropical and sub-tropical climates.
In drink mixing, fresh lemon juice brings a tangy zing to so many classic drinks and in fact, it's the most used ingredient in drink mixing other than the liquors of course.

Water

Water might seem like one ubiquitous ingredient in any alcoholic beverage, and to have no specific purpose other than dilute the alcohol, to prevent irritation and burn, it has more purpose to its presence than it seems.
Water breaks the alcohol molecules and attaches to them and releases the esters that holds the secret to the aroma into the drink and to the nose. Temperature of water is important and although almost all cocktails are served chilled, be sure to understand the role water plays in a drink. Another factor is the quality of water, if you are serious about your cocktail, be sure to use the best neutral tap water or preferably bottled spring water if possible.

Sugar

Brown Sugar is a sucrose sugar with a distinctive brown colour from the presence of molasses, it is a partially refined or unrefined sugar containing sugar crystals and residual molasses giving it a distinctive taste and flavour of crystallised molasses or toffee. The taste of dark brown sugar is described as a caramel taste with a deep molasses flavour.
Brown sugar is used in cocktails where a caramel candy or toffee flavour is expected.

Caster Sugar is finely ground granulated sugar. It is not as fine a powdered confectioners' sugar and has a little grit to it. It is somewhere between confectioners' sugar and granulated sugar, and melts in mouth with a mild spicy feel to the tongue

Vanilla Sugar is the regular granulated sugar infused with vanilla flavour, by using vanilla pods and seeds to flavour the sugar. A home made alternative is to use vanilla sticks or pods in a jar of sugar and leave it sealed for 4 weeks to allow the vanilla flavour to infuse. Or to use granulated sugar and vanilla extract and blend in a mixer, although this ends up in powdered sugar.