You can use sleeper to indicate how well someone sleeps. For example, if someone is a light sleeper, they are easily woken up.

In British English, a sleeper is a carriage on a train containing beds for passengers to sleep in at night, or a section of such a carriage. The usual American words are sleeping car for the carriage and roomette for the section.

A sleeper is a train with beds for its passengers to sleep in at night.

Railway sleepers are large heavy beams that support the rails of a railway track.

If you describe someone or something as a sleeper, you mean that they unexpectedly become successful, often after a long period of being inactive or unknown.