It's a 15-minute bike ride. Similarly: He's an eight-year-old boy. That's a two-meter-high wall. That's a four-floor building. (or That's a four-storey building.) More information: https://www.thoughtco.com/hyphen-punctuation-term-1690944 [excerpt] As a general rule, compound adjectives that come before a noun are hyphenated (for example, "a coffee-colored tie"), but compound adjectives that come after a noun are not hyphenated ("My tie was coffee colored"). Hyphens are usually omitted with commonly used compound adjectives (such as "the tax reform bill") and with adjectives preceded by adverbs ending in -ly ("an oddly worded note").

No apostrophe.

By the way, I have to say that your sentence above is still wrong. You should put the indefinite article "a" ahead of "15 minutes' bus ride".

I know that "It is a 15-minute bus ride." is absolutely correct, though I suppose you can also say "It is a 15 minutes' bus ride.". I am sure that you can easily see that many native speakers of English actually say that way if you just google for it.

https://english.stackexchange.com/questions/280155/which-is-correct-use-of-the-apostophe-in-minutes