Is anyone able to please help me find the hadith in which Rasoolullah SAW stated that the believers will be asked about each luxury they have had in this world, even a cold glass of water?
Perhaps you have this in mind:
إن أول ما يسأل عنه يوم القيامة - يعني العبد من النعيم - أن يقال له: ألم نصح لك جسمك، ونرويك من الماء البارد
Indeed the first of what will be asked about on the Day of Judgment – meaning the slave (of Allah) being questioned about the favors – is that it will be said to him: ‘Did We not make your body, health, and give you of cool water to drink?
It is narrated in the exegesis of the verse:
ثم لتسألن يومئذ عن النعيم
Then you will surely be asked that Day about pleasure.