How can this rails controller test be cleaner refactored?
shared examples share the let scope, so you could further dry up your code (assuming you use do_action for every action) to this:

shared_examples :empty_success_response do

  before do
    do_action
  end

 ...
end


Also, if you are using do_action, I also like to add to my scopes:

describe '#destroy' do
  let(:do_action) do
    delete :destroy, id: subject.id.to_s
  end

  after do
    do_action
  end

  ...
end


This way, you don't have to call do_action if all you do in the test is set expectations. 

it 'makes the call' do
  expect(controller).to receive(:destroy_item).once.times.with(subject.id.to_s)
end


If in some tests you want do_action to run before the end of the test - that's no problem, since let runs the code only once - so it won't run again at the end of that specific test!