By legal definition, pastis is described as an anise-flavored spirit that contains additional flavor of licorice root, contains less than 100 grams/l sugar, and is bottled at a minimum of 40% ABV (pastis) or 45% ABV (pastis de Marseille).

To enjoy Pastis, serve 2 ounces of the liqueur in a small Collins glass with a pitcher of mineral water on the side. ... The reason you dilute Pastis is because it's 45 percent alcohol, so drinking it straight would be like sipping on a glass of gin.