Applications as well as environments can be easily deleted.
To delete an environment go to the Application Catalog > Environments index page and click "More" -> "Delete Environment" in Actions column of ready to delete environment.
Environment deletion means to kill all services with instances on which they are installed. Instances will be scheduled to delete right after you choose the "Delete Environment" action.
To delete an application go to the application list page and click the "Delete Service" button in Actions column. Note: If you are deleting application that was already deployed you'll need to Deploy the environment again by pressing corresponding button. In case you want to delete application prototype - it has "Service draft created" in the Last operation column (see the screenshot below) - changes applies right away.