English Translation
Just a spot of shut-eye has already refreshed my mind.
I don’t say さっぱりした in this context. すっきりした or スッキリした would be much better. さっぱりした is more often used for physical cleansing such as washing dirty hair or drinking sparkling water to get rid of greasy taste in your mouth. スッキリした, on the other hand, is more suitable when you have “brain fog” (mentally). The fog can be due to either an anxiety or puzzling question.
TTS is correct but the transcript is incorrect. 一寝入り should be pronounced as ひとねいり, not いちねいり.
FYI: 寝入る (verb) means “to fall asleep”. Attached with 一, 一寝入り (noun) means “a quick nap”, and 一寝入りする (verb) is “to have a quick nap”.
一寝入り is completely interchangeable with 一眠り / ひと眠り（ひとねむり）.