When Elim Garak's cranial implant began to malfunction in 2370, he began to drink an excessive quantity of kanar in an attempt to mimic the implant's numbing effect using the alcohol. (DS9: "The Wire")
It was possible for Kanar to spoil, something which apparently happened to two bottles of it Quark tried to give to Ulani Belor and Gilora Rejal in 2371. Shortly afterwards, Morn took ill from food poisoning, and suspected that a free glass of the drink at Quark's was to blame. (DS9: "Destiny")
Shortly after the Klingon invasion of the Cardassian Union in 2372, Quark had 80 cases of kanar in his stockroom. Quark gave a bottle of it to Garak "on the house" because he did not foresee ever selling it in his bar again. (DS9: "The Way of the Warrior")
Tekeny Ghemor, while spending his final days on DS9 began giving away secrets of the Cardassian government; to try and stop this Dukat and Weyoun tried to poison him with a bottle of kanar laced with Voraxna poison. Weyoun drank a glass of the poisoned kanar and found it to be quite toxic, explaining the Vorta were immune to most poisons. (DS9: "Ties of Blood and Water")
Damar was fond of indulging in kanar, especially the 2327 vintage. Quark used it to great success as the inebriated Damar revealed that the Bajoran minefield was about to be brought down. (DS9: "Behind the Lines") Later, he often drank to excess during his humiliating tenure as head of the Cardassian Union in 2374-2375 - so much so that, after giving up the spirit as he planned his revolt against the Dominion, Weyoun joked about how different he looked without a bottle in his hand. He began storing empty bottles in his quarters. Upon seeing them, Dukat encouraged his former subordinate to be strong. (DS9: "'Til Death Do Us Part", "The Changing Face of Evil")
Background Information Edit
In DS9: "The Way of the Warrior", it appeared differently again, this time it was an orange, opaque liquid, but served in the characteristic kanar bottles. After that, it finally changed back to the black, thick liquid seen for the first time in "The Maquis, Part II".
According to an interview with Casey Biggs (Damar), Karo syrup was used for brown kanar to create the effect of a dark, thick liquid, which he actually drank. Property Master Joe Longo joked in an issue of Star Trek: The Magazine (Issue 4) that "... he was drinking so much he was getting weird, so we started using a thickened sugar-free pancake syrup."
Damar's fondness for the spirit, first observed in "Behind the Lines", was introduced as a way to show an inner turmoil, essentially using it to drown out his conscience and justify an alliance he knows to be wrong – indeed, in "Strange Bedfellows", he looks at himself in the mirror and tosses the drink at his reflection just before helping Worf and Dax escape. (Star Trek: Deep Space Nine Companion)
In "Behind the Lines", Kanar appeared as a much thinner liquid, akin to many Human beverages such as wine or spirits. This is in contrast to "Defiant" where Dukat was shown pouring the drink while being briefed by Sisko and Odo, where it appeared to have a thick, treacle-like consistency. The thinner liquid was of an older, expensive vintage, leading to the conclusion Kanar may thin out as it ages.
The strength of Kanar may also vary greatly. In many episodes we see Cardassians drinking multiple bottles of it like it was wine, while in "Behind the Lines" Quark and Damar are both rendered drunk by sharing a single bottle; considering that they are a bartender and a soldier they're both expected to have great drinking stamina which suggests that this bottle of expensive Kanar had the strength of a hard liquor (which also explains the thinness of it as alcohol has a very low viscosity).