Paradise Killer

There are a total of 23 drinks needed for the unlock. Drinks can be purchased by entering it's code(letter and number) from the vending machines that spread throughout the map, Each machine has one special drink and can be purchased using 1 red crystal, Red crystals are very common and can be collected in minutes.
You need starlight upgrades to access some machines for example the one in dead zone.
My advice is to first focus on getting the starlight upgrades(to open doors) and footbaths upgrades(to navigate the map easily).
You can view the drinks you have by opening starlight>inventory>relic and compare them with the list below to see what you are missing.
-The game trackers are working and it will goes up by 4-5% with each drink you collect.
After buying a drink.. the machine light will turn off, you can use this as a sign for the already used machines. you can also use meditation ability and the vending machines will appear as a collectable if it wasn't already collected
List of drinks in alphabet:
Acid's Favorite
Aethestic Water
Angel Ward
Bizarre Lychee
Blood Fountain
Cool Melon
Crystal Sparkling Water
Dead Moon
Evening Haze
Indefinable Spectrum
Kill The Thirst
Lost Mountain Water
O.O.O.
Parallel Red
Parasol
Pillar Flower
Power of Goat Soda
Provocative Flower
Sanitea
Statue Mind
The Elusive Chocolate
Tropical Demolition
Water

I found a cool list of vending machine locations depending on the area. All credit goes for neoseeker/owners of this great list.

https://www.neoseeker.com/paradise-killer/walkthrough/Vendin...

After collecting all of the drinks you will get a call and new starlight skin.