The Usual Suspects

• The most common liquors, such as vodka, tequila, rum and bourbon, can all go in milkshakes when paired with the appropriate flavors. Both vodka and rum go well in milkshakes in which you want the booze to take a backseat to the other ingredients; vodka pretty much disappears into the shake, while rum adds mostly sweetness to the drink. Bourbon and tequila both add a little bite to your milkshakes; bourbon is best in milkshakes with lighter flavors like vanilla and caramel, while tequila brings out the spices in chocolate and cinnamon milkshakes.

Liqueured Up

• Liqueurs, which are lower proof liquors with higher concentrations of sugar, also blend well in milkshakes. Liqueur flavors include many fruits, such as banana, orange, strawberry and melon; herbs and spices like peppermint, cinnamon and anise; and specialty flavors, like butterscotch, coffee and chocolate. If you prefer fruit-flavored and herbal or spiced liqueurs, add them to more subtle ice creams like vanilla or complementary flavors like strawberry, peach and blueberry. Specialty liqueurs, as well as some herbal liqueurs, work well in milkshakes with proven flavor combinations, such as mint liqueur in a chocolate shake or chocolate liqueur in a coffee shake.

Creamier and Creamier

• A few liqueurs fall into the special category of cream liqueurs; the dairy added to these liqueurs gives them a creamier texture and a more dessert-like taste. The most well-known cream liqueur for milkshakes is Irish cream, which has Irish whiskey as its base. Other cream liqueurs that will make your milkshakes deliciously adult include toffee, chai tea, tequila and maple cream liqueurs. Add cream liqueurs to milkshakes with similar ingredients, like Irish cream, which has hints of cocoa, to a chocolate milkshake. Cream liqueurs may also substitute for some or all of the milk in your shake.

A Softer Side

• Other lighter boozy beverages, like beer and wine, can also help in turning your shakes into adult treats. Darker and stouter beers add more flavor and substance to your shakes; add some Irish stout to your vanilla milkshake or vanilla porter to your chocolate shake. Red wine like pinot noirs work well in richer milkshakes blended with dark chocolate; sweet whites and even sparkling varietals add booze and balance to fruitier shakes. Port, which is fortified wine, complements basic shakes like strawberry or chocolate with some added fruit such as figs or dates.