Fireball

The primary characters are perfect replicas of each other. Without further ado we can deduce that Miss Monochrome and Drossel von Flügel are in fact androids with an obsession towards black and white color theme. Their AI as well is expanded upon learning more and more about humans whether it is done through direct interaction with them, as seen through the struggles of Monochrome trying to become an idol, or trivia given by their closest friend, robot Ruu-chan in Monochrome's case and Gedächtnis for Drossel. Because they are both short and episodic in content, don't expect much. 

Both are comprised of 2-4 minute shorts of character-based situatational comedy in a consistent setting.  

Although Sonic's CGI and animation level are ALOT higher then Fireball's, but both are highly enjoyable CGI short, Sonic is an 11-minute ONA, while Fireball's a 13-episode series (somewhere around 25 minutes total). Both quick fixes which you will certainly enjoy. 

Both anime's deal with similar dialogue's, namely, funny dialogue's which mean nothing in the end. Also both these anime's only deal with CGI and not drawn animation. 

Different themes and style (CGI and Drawn), but both deal with a lot of sarcastic, stupid, random and hilarious scenes. And that's the way they are similar, through their "stupid" humor. 

Both are series of humorous short films (about 2 minutes per episode); both deal with robots; both are "just for fun".