Irradiated whiskey is an addictive alcoholic drink which when consumed provides a minor status boost - increasing Charisma and Strength by one while reducing Intelligence by one. Irradiated whiskey, as the name suggests, is a radioactive variant of whiskey - presumably produced when normal whiskey has been exposed to large amounts of radiation for an extended period. Thus, it will also impart 10 units of radiation.
As with most alcoholic item in Fallout: New Vegas, irradiated whiskey's effects (both positive and negative) are altered by the player's Survival skill. With a Survival skill of 100 the player will receive +3 to Charisma and Strength, -3 to Intelligence, and +30 radiation.
In hardcore mode irradiated whiskey will increase the player's level of dehydration. This effect is also affected by the Survival skill, ranging from +25 at lower levels to +75 at 100 Survival skill.
Effects of Survival skill
+1 Charisma, -1 Intelligence, +30 Dehydration
+2 Charisma, -2 Intelligence, +55 Dehydration
+1 Charisma, -1 Intelligence, +35 Dehydration
+2 Charisma, -2 Intelligence, +60 Dehydration
+1 Charisma, -1 Intelligence, +40 Dehydration
+2 Charisma, -2 Intelligence, +65 Dehydration
+1 Charisma, -1 Intelligence, +45 Dehydration
+2 Charisma, -2 Intelligence, +70 Dehydration
+2 Charisma, -2 Intelligence, +50 Dehydration
+3 Charisma, -3 Intelligence, +75 Dehydration
Note: radiation levels are not affected by the Survival skill level.
Whiskey Rose is a perk provided while Cass is serving as a Companion in the player's party. With this perk the penalty to Intelligence for consuming any type of alcohol is eliminated, as are the effects of alcohol addiction. However, it will still be considered radioactive, and will apply radiation to the player as normal.
A fourth bottle may be found inside a refrigerator inside Hell's Motel. This fridge is set to contain four of a random selection of irradiated foods, including irradiated whiskey. There is only a 29% chance of any specific food item appearing in that refrigerator, including irradiated whiskey.
There is a refrigerator in an impact crater in the Big MT that may contain a bottle, along with some other irradiated food.