The Cleanse (2016) on Netflix

Plot summary

Paul Berger has lost his job and his fiancée and is depressed when he attends a selection seminar. The program on offer is Let's Get Pure, a secretive self-help course run by Ken Roberts. There he takes an interest in a fellow applicant, Maggie Jameson. Paul is picked for the program's purification retreat. A liability waiver warns of possible death, and he hesitates, but he signs once he hears Maggie was picked as well. A car brings him to a secluded woodland site, where Fredericks, part of the program for weeks, is already living. Paul and Maggie also meet Eric and his girlfriend Laurie, two more applicants who were chosen. Lily leads the sessions, and each newcomer receives four individually mixed cleanse drinks to consume before the first day is over.