Locations for all 48 juice boxes. 9 are missable and 39 non-missable, and you need 40 for the achievement. So you have to get at least one missable to get the achievement. The juice boxes you get as reward in the DLC arena does not count toward the achievement.

If you only care about the missables, I will list them here, they are also included in the main portion of the guide:

Adam - Apple Juice - Lydia's House, house will be locked later in the game.
Dradora North - Spinach Juice - Jail, will be blocked later in the game.
Borges - Carrot Juice, Spinach Juice, Broccoli Juice - During the sneaking section.
Blackrot's Ship - Carrot Juice - In the room you start in.
Passageway - Broccoli Juice, Carrot Juice, Apple Juice - In open boxes near the tracks.

Spinach Juice - Kellan's House
Broccoli Juice - Kellan's House
Apple Juice - Lydia's House (MISSABLE)
Carrot Juice - Armor Shop

Apple Juice - Witch's House
Spinach Juice - Witch's House

Carrot Juice - Zak and Nik's Place

Apple Juice - Inn
Spinach Juice - Barrel in south-west corner.

Carrot Juice - Near the start of the area

Broccoli Juice - Up the stairs to the northwest

Broccoli Juice - Inside the house near the previous juice

Apple Juice - Inside guardhouse

Spinach Juice - Crate in jail (MISSABLE)

Apple Juice - Den, can only be accessed after getting the Airship

Carrot Juice - Den, can only be accessed after getting the Airship

Carrot Juice - During stealth section (MISSABLE)
Spinach Juice - During stealth section (MISSABLE)
Broccoli Juice - During stealth section (MISSABLE)
Apple Juice - Tavern
Spinach Juice - Inside the docks storage room
Carrot Juice - Out on the east pier, not accessible until getting the airship

Carrot Juice - In the room you start in (MISSABLE)

Broccoli Juice - Barrel next to the northern house
Spinach Juice - Inside the northern house
Carrot Juice - Barrel behind western house
Apple Juice - Inn, lower floor
Broccoli Juice - Western house, lower floor. Only accessible after getting the airship.

Spinach Juice - Box
Broccoli Juice - Barrel

Broccoli Juice (MISSABLE)
Carrot Juice (MISSABLE)
Apple Juice (MISSABLE)

Apple Juice - First cave directly south from the start of the area.

Broccoli Juice - Cave with two entrances.

Spinach Juice - Cave with two entrances.

Apple Juice - On the way up the tower.
Broccoli Juice - On the way up the tower.
Carrot Juice - On the way up the tower.
Spinach Juice - Tower, downstairs.

Carrot Juice - Near where you rescued captain Blackrot
Apple Juice - In the cell you were inprisoned in, can only be acquired once you have the airship.
Spinach Juice - In the shop, can only be acquired once you have the airship.

Just a reminder for the juice boxes you couldn't access before getting the airship.

Dradora North - Apple Juice - Den
Dradora North - Carrot Juice - Den
Borges - Carrot Juice - East pier
Brashear - Broccoli Juice - Western house, downstairs.

Spinach Juice - Box

Broccoli Juice - Cave to the west, barrel.
Carrot Juice - Cave to the west, box.

Carrot Juice - In the first cave.
Broccoli Juice - In the house.

• Myself for creating this guide.
  
• Vance Finiraldi for posting juice locations on the forum, which was a helpful starting point for creating this guide.
  
• And of course Something Classic Games[www.somethingclassic.net] for creating the game.