apt-get. It simply tells you what it's going to remove/install.
Calling an API to retrieve data is not really the type of program that requires a dry-run flag. It's mainly useful for commands that change the state of something in ways that could potentially be destructive, unwanted and/or hard to revert.
If you call an API to retrieve data, how can that be a dry run? Are you suppose to give fake examples with fake output?