Anyone who's ever mentioned an Apple product in a tweet has probably been on the receiving end of a torrent of replies from spambots. Oh the humanity. Fortunately, Twitter makes it easy to report spam--and other, more serious abuses.
To report an abusive tweet, go to the tweet in question--either through a direct link to the tweet or by finding it in your Twitter timeline or another user's profile page--then look for the More button in the lower left corner of the tweet and click it. You may need to hover your mouse over the tweet for it to show up.
From the resulting menu, select Report Tweet. Twitter will pop up a box asking you to specify whether the tweet is spam, whether that person's account was compromised, or whether it violates another rule ("Abusive").
Select the appropriate button, select whether you want to block and unfollow the account in question, then press Submit. If you selected "Abusive" from the list, the Submit button changes to a Next button, and Twitter will ask you for additional information on why you think the tweet is a problem.
Blocking someone with the Twitter smartphone app
The process works much the same on Twitter's mobile app. Tap any tweet in your timeline, tap the More button (represented by three dots), then tap Report Tweet.
The app will then ask you to detail what the problem is and step you through the reporting process from there. Once you've selected the appropriate option, tap the Submit button. If you report an abusive tweet, the Submit button will turn into a Next button. Tap it, and Twitter will ask you some additional questions about the tweet in question.
After you make a submission, Twitter will review your report and take action against that user if necessary. Be patient, though--Twitter might not address the problem immediately. Blocking the account can give you some peace in the meantime.