To update multiple participants of a tournament you can use Toornament::update_tournament_participants method:

extern crate toornament;
use toornament::*;

fn main() {
    let toornament = Toornament::with_application("API_TOKEN",
                                                  "CLIENT_ID",
                                                  "CLIENT_SECRET").unwrap()
                                .timeout(5);

    // Define participants
    let mut participants = vec![Participant::create("First participant"),
                                Participant::create("Second participant")];
    // Update a participant for a tournament with id = "1"
    let new_participants = toornament.update_tournament_participants(TournamentId("1".to_owned()),
                                                                     Participants(participants));
}

This will update a list participants by replacing all old participants with new ones.

Via iter-like interface:

extern crate toornament;
use toornament::*;

fn main() {
    let toornament = Toornament::with_application("API_TOKEN",
                                                  "CLIENT_ID",
                                                  "CLIENT_SECRET").unwrap()
                                .timeout(5);

    let participants = toornament.tournaments_iter()
                                .with_id(TournamentId("1".to_owned()))
                                .participants()
                                .edit(|_| {
                                    Participants(vec![Participant::create("First participant"),
                                                      Participant::create("Second participant")])
                                })
                                .update();
}