"The beverage has a bad taste."
Translation:למשקה יש טעם רע.
As for salt, salty:
Salt is mélakh מלח and salty is מלוח malúakh. This is another pattern and refers to something which has received an action, e.g. פתוח patúakh is something that has been opened, so it is the adjective “open”. מלוח is (theoretically) something which has had salt added to it but it’s used even for things that are naturally salty.
This particular word is part of a set called the katil pattern. Please see https://en.m.wiktionary.org/wiki/Appendix:Hebrew_patterns/קָט%D6%B4יל
However, these are quite specific and completely new adjectives according to this pattern are only possible with the second meaning listed there, that of “-able”. E.g. חפיש khafís searchable, a very recent addition to the language, is from חיפוש khipús search (noun) or לחפש lekhapés to search (verb).
In general, adjectives are formed by adding י to the end: שימוש shimúsh use (noun), שימושי shimushí useful.
This way of forming adjectives is very productive, and I could therefore invent חיפושי khipusí, “search-related”, and it would be understood readily.
My understanding is because of the word 'has.' In Hebrew, there's no direct translation for to have, so you'd have to say "there is to me/him/her/etc." In this example, the literal translation would be "To the beverage there is a bad taste," just like how יש לי משקה would literally translate to "There is to me a beverage." In both cases, the -ל prefix means 'to.' I believe beginning with the ה would mean "The beverage there is a bad taste," which doesn't make sense, because יש doesn't really translate to have/has, it's more like 'there is.' Hopefully that makes sense!