There are several common sources of sour flavors in cocktails:

• Citrus juices - lime, lemon and orange are the most commonly used citrus juices in cocktails. They add a bright, acidic flavor to the drink.

• Ripe mangoes and pineapples - provide both sweet and sour flavors to cocktails.

• Green mangoes - when burned and liqufied is called Aam Panna, add a complex sour flavor to cocktails.

• Chaat Masala - a complex spice mix, often including amchoor

• Phuchka water - a sour liquid containing chaat masala, tamarind juice, cumin powder, gondhoraj lebu, and other spices.

• Tamarind - a sour fruit that is commonly used in cocktails like the Margarita.

• Tart fruits, like cranberries, raspberries, and pomegranates are commonly used in cocktails like the Cosmopolitan.

• Vinegar - a sour liquid that is commonly used in cocktails like the Bloody Mary. It’s important to use a high-quality vinegar, such as apple cider vinegar when making cocktails to ensure a good flavor.

• Pickles - a sour vegetable that is commonly used in cocktails like the Vodka Gimlet.

• Fermented ingredients - some cocktails use fermented ingredients like kombucha or kefir to add sour flavors.

• Sour mix - a pre-made mix of citrus juices, sugar, and other ingredients that is often used to add sourness to cocktails.

• Acidulated juices - juices that have been treated with an acid like lemon juice or vinegar to give them a sour flavor.

• Shrubs - a type of syrup made from fruit, sugar, and vinegar that is used to add sourness to cocktails.

• Bitters - a type of aromatic flavor extract that is used in small quantities to add depth and complexity to cocktails. Some bitters, like Angostura, have a slightly sour flavor.

• Sour candies - a sour candy that is commonly used in cocktails like the Whiskey Sour.

• Sour cream - a sour dairy product that is commonly used in cocktails like the White Russian.

• Vermouth - a fortified wine that is commonly used in cocktails like martinis and manhattans. It has a slightly sweet and sour flavor.

It is perfectly fine to use multiple sour sources in a cocktail. E.g. if the primary source of sourness in a cocktail is a mango juice, a small amount of lime juice can add extra richness and complexity to the drink. If you are making a Whiskey Sour, you can use both lemon juice and sour candies to add sourness to the drink. If you are making a Bloody Mary, you can use both tomato juice and vinegar to add sourness to the drink. If you are making a Cosmopolitan, you can use both cranberry juice and raspberries to add sourness to the drink.