promise (someone) the stars

Translations
давать (кому-то) нереальные обещания
He promised her the stars, but in reality, he couldn't even keep simple commitments.
Он дал ей обещания, которые были невыполнимыми, но на деле не мог выполнять даже простые обязательства.
Definitions
To make extravagant or unrealistic promises to someone, often suggesting that you will give them anything they desire, even things that are impossible or highly unlikely to obtain.