turkish is different from english in this case. bu şişede is in this bottle. -ki suffix makes 'bu şişede' an adjective. 'bu şişedeki' defines 'su', it is an adjective and it is written before the noun because it is an adjective. another example for it:
bahçedeki araba çok eski( the car is in the garden is very old)
Adjectives need to come before whatever they modify, so "tuzlu su" is going to have to most typical meanings -- "salty water" and "saltwater."
When you see "su tuzlu" -- it's not so much that the "tuzlu" comes after "su" -- but that it comes before the verb, in the role of a manner-adverb, like if you were eating/drinking/ordering something "with salt."
That sentence was about wine "which is here in the bottle" (lit. which is in the bottle which is here) -- a double-layer of -ki location-adjectives. In this sentence "bu" is only determiner, and a 2nd -ki wouldn't make sense (which is in the bottle which is this...?).