What is the easiest way to capture the SQL statement for a Report Builder report you're troubleshooting?

Run Profiler
Profiler will work as long as you have permissions to profile the server and is the the best solution because it requires no change to the Report Server itself. There is a way to log all report SQL to a log file, but that option was not listed here and is better used if you want to do analysis rather than troubleshooting.