He, like all the rest, fell fast asleep in a moment.
He then drank off a cup of rakee, and rolling over in a state of stupid intoxication, fell fast asleep.
I swam on shore, and got into a cave, where I fell fast asleep.
The nightingale was pouring forth her sweet melody, and friendly to lovers, she continued it until Mezrimbi, who had listened to it, and whose angry feelings had been soothed with her dulcet strains, fell fast asleep.
The above list will hopefully provide you with a few useful examples demonstrating the appropriate usage of "fell fast" in a variety of sentences. We hope that you will now be able to make sentences using this group of words.