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.

Lemon Juice

Lemon 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. Lemon juice is known to reduce or even reverse the effects of excessive alcohol consumption and intoxication.
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.

Bourbon Whiskey

American's don't need to be lectured on Bourbon, but still, let's put it in record like all other spirits. A Bourbon in American spirit is a barrel-aged distilled liquor made primarily from corn. The name might have been derived from the French Bourbon dynasty, or from Bourbon County in Kentucky, or Bourbon Street in New Orleans, both named after the French Dynasty.

Technically, most whiskey made in America are legally classified as Bourbon, although Bourbon is in spirit a Southern Whiskey with special connection to Kentucky. Note than although Tennessee Whiskey is classified as Bourbon, Tennessee distilleries do not prefer their whiskey to be unique and referred to as Tennessee Whiskey only.

Distilling came to Kentucky in the late 18rth Century with the Scots, Scot-Irish and other settlers including English, Welsh, German and French, and they brought with them their distilling techniques and ageing processes in charred oak barrels. The charring is what gives the Bourbon the brownish colour and distinctive taste.

To be a legal Bourbon, a whiskey has to meet the following criteria

Produced in the United States and Territories (Puerto Rico) and the District of Columbia
Made from a grain mixture that is at least 51% corn
Aged in new, charred oak containers
Distilled to no more than 160 (U.S.) proof (80% alcohol by volume)
Entered into the container for aging at no more than 125 proof (62.5% alcohol by volume)
Bottled (like other whiskeys) at 80 proof or more (40% alcohol by volume)

Kahlua Coffee Liqueur

Coffee liqueur is a liqueur produced by steeping roasted coffee, sugar and other ingredients in neutral spirit. The most famous coffee liqueur brands are Kahlua and Tia Maria, Kahlua has been made in Mexico since 1936.

However Kahlua has a thick buttery taste, that doesn't always appeal to the preferences of an alcoholic beverage lover. Which is why many people enjoy coffee liqueur made using their own home recipes.

Typical ingredients of coffee liqueur include liquor, espresso coffee, roasted coffee bean (and powder), sugar, and vanilla syrup.

The characteristic flavor of coffee along with over a couple of hundreds compounds contribute to the taste of coffee liqueur. Caffeine is a major ingredient of coffee, and also might be a taste factor that influences the complex flavour profile that appeal to coffee liqueur drinkers' palate. Reference - International Journal of Engineering & Advanced Technology (IJEAT)

NOTE: In the absence of a Coffee Liqueur like Kahlua or Tia Maria, to make cocktails with Coffee Liqueur, Coffee Liqueur Syrup can be used as a substitute with the proportionate alcohol substituted with a triple distilled neutral Vodka.