Inside controller inject Request object. So if you want to access request body inside controller method 'foo' do the following:
public function foo(Request $request){ $bodyContent = $request->getContent();}
You can pass data as the third argument to call(). Or, depending on your API, it's possible you may want to use the sixth parameter.
call()
From the docs:
$this->call($method, $uri, $parameters, $files, $server, $content);
For those who are still getting blank response with $request->getContent(), you can use:
$request->getContent()
$request->all()
e.g:
public function foo(Request $request){ $bodyContent = $request->all();}