Cassis liqueur has a distinctive flavor that makes it a favorite among mixologists. Here it is mixed either with rum or with soda, such as Seven Up (or you could try it with lemon-lime seltzer). And here's another tip: Dip the rim of the glass in water to moisten, or rub with a lemon or lime wedge, and then dip it into coarse or brown sugar to coat, so you get a little sugar as you sip the drink.