Collectibles achievements, there is 7 blue bottles :
Chapter 1 : In Pierce's Office, hard to miss
Chapter 2 : In the Hawkins' Warehouse
Chapter 3 : In the Hawkins' Manor, during the investigation, it's in the Simon's room
Chapter 5 : In Riverside Institute, near the kitchen (related to the Sandman Achievement)
Chapter 6 : In Sanders' Manor, on his desk (the room before the Shambler painting)
Chapter 7 : In Algernon's bookstore, in a drawer.
Chapter 9 : In Dr. Fuller's Office.
Congrats you won an achievement.