Games like The Sleep Experiment
Games like The Sleep Experiment include SOMA, Poppy Playtime, Sally Face - Episode One, Outlast, and Darkwood. We matched them by the tags players give The Sleep Experiment on Steam (Indie, Horror, Psychological Horror, Survival Horror, and Dark): closest matches first, and among equally close ones the better-known games.

SOMA
Shared: Horror · Psychological Horror · Dark

Poppy Playtime
Shared: Horror · Survival Horror · Psychological Horror

Sally Face - Episode One
Shared: Indie · Psychological Horror · Horror

Outlast
Shared: Horror · Survival Horror · Psychological Horror

Darkwood
Shared: Horror · Survival Horror · Psychological Horror

Little Nightmares
Shared: Horror · Adventure · Indie

Amnesia: The Dark Descent
Shared: Horror · Psychological Horror · Survival Horror

Little Nightmares II
Shared: Horror · Adventure · Dark

No, I'm not a Human
Shared: Horror · Psychological Horror · Indie

Outlast 2
Shared: Horror · Psychological Horror · Survival Horror

Visage
Shared: Horror · Psychological Horror · Survival Horror

Five Nights at Freddy's
Shared: Horror · Survival Horror · Indie

Layers of Fear (2016)
Shared: Horror · Psychological Horror · Indie

What Remains of Edith Finch
Shared: Story Rich · Mystery · Indie

Inside the Backrooms
Shared: Horror · Survival Horror · Psychological Horror

Amnesia: A Machine For Pigs
Shared: Horror · Psychological Horror · Story Rich

Penumbra Overture
Shared: Horror · Indie · Survival Horror

Mouthwashing
Shared: Horror · Psychological Horror · Indie

Lethal Company
Shared: Horror · Survival Horror · Psychological Horror

Bendy and the Ink Machine
Shared: Horror · Indie · Survival Horror

SILENT HILL 2
Shared: Horror · Psychological Horror · Survival Horror

Amnesia: Rebirth
Shared: Horror · Story Rich · Adventure

Five Nights at Freddy's 2
Shared: Horror · Survival Horror · Psychological Horror

Still Wakes the Deep
Shared: Horror · Psychological Horror · Dark