How does one pronounce "11.53 cups"?

Question

I am uncertain how to handle the combination of the fraction, counter, and rendaku.

Is it じゅういっぱいてんごじゅうさん or maybe じゅういちてんごじゅうさんばい?

It occurred in this sentence here:

全日本【ぜんにほん】コーヒー協会【きょうかい】の2020年【にせんにじゅうねん】の調査【ちょうさ】によると、国内【こくない】で1週間【いっしゅうかん】に飲【の】まれるコーヒーの量【りょう】は1人【ひとり】あたり11・53杯【??】

According to a 2020 survey by the All Japan Coffee Association, the amount of coffee consumed per person per week in Japan is 11.53 cups.

https://www.asahi.com/articles/ASQ9D316ZQ8LPLBJ00S.html?iref=comtop_International_01

Answer 1

Usually it's

じゅういち てん ご さんばい

or

じゅういち てん ご さんはい

The digits in the fractional part are pronounced one by one, and rendaku with the counter at the end concerns the one digit before it immediately, just like in 3杯 and 23杯, which share the same さんばい/さんはい. You don't cluster digits past the decimal point to find a two-digit number.(*)

The counter doesn't move around to avoid the fractional part. You can see 1.5杯 and say something like いっぱい と はんぶん（一杯と半分）, but that's more like interpreting than reading.

One bonus point: single-syllable numbers before the decimal point can often be elongated, as in 2.3 - にー てん さん instead of に てん さん.

(*) Usually, that is. Some groups of people in specialized fields might have other ways to read it that involve clustering, like the one you gave, but that's not the norm.

EDIT: There is an important exception. if there is a subunit that would follow, as in centimetre for metre, that can affect how you read a number with the main unit, at least colloquially. For example, "1.53m" can be いち メートル ごじゅう さん, colloquially, omitting "centimetre". (This too might be more of interpretation, though.) Also colloquially, "1." can be いってん, as Darius Jahandarie said below.