Heraklion has a remarkably vivid nightlife and, as such, alcohol consumption cannot be avoided. Be careful of adulterate drinks that can easily lead to intoxication. It is safer to order a bottled or try your favorite drink, of which you know the taste.
Another option is the cinema. Watching a movie in an open, summer theatre, under the starry night with the scent of jasmine diffused in the air, is surely a must!
And, if you don’t mind crowded places, on Saturdays in the city the open air market is held. The local producers behind the kiosks sell almost everything, from fruits and vegetables to clothes and electrical items.