To use bundler with a Sinatra application, you only need to do two things. First, create a Gemfile.
Then, set up your config.ru file to load the bundle before it loads your Sinatra app.
require 'bundler' Bundler.require require './my_sinatra_app' run MySinatraApp
Start your development server with rackup, and Sinatra will be loaded via Bundler.
$ bundle exec rackup