The REV UP study is testing two different ways to prevent HIV. One option is an on-demand rectal douche with tenofovir (a medicine for HIV prevention), and the other is the regular oral pill (PrEP) people take before sex. The goal is to see how safe and acceptable the rectal douche is compared to the pill and to find out which one people prefer. This study will help decide if the douche could be developed as a new option for preventing HIV.