i'm looking for an useful application/plugin that connects Jira and SugarCRM.
We're using Sugar Prof. 8.X.
There is a 3rd party plugin available on SugarExchange that you could test to see if it meets your requirements:
Other than that you could look into using the APIs of Sugar and JIRA to connects the two, for example by creating a middleware integration that syncs the data in between.
Sugar <------------> Middleware <-------------> JIRA
Sugar REST API JIRA API
You'll find examples how to work with data in SugarCRM using the REST API here:
Hope that helps,