Chicchana Yukitsukai Sugar

Both dealing with fairies and the human world both including humans and both very cute animes.i would recommend this because i officially love fairies and both have simillar concepts. 

Both have fairies who must team up with humans to graduate, both are cute and suitable for children. 

both have little fairy and they turn into more powerful fairy 

The greatest strength of Cardcaptor Sakura is its character development. A series about a magical girl collecting cards does not seem like it would have a deeper story behind it, but it does. The same is true for Sugar. A series synopsis will tell a viewer that Sugar is about a snow fairy hoping to become a fully realized season fairy by searching for the kirameki, and a human named Saga helps her and her friends along the way. One might expect an episodic storyline about childish trials and moral lessons, but the storytelling gets much more involved. And character development shines through as a result. Cardcaptor Sakura, for its time, had high-quality animation and a diverse soundtrack to keep the viewer's attention. Sugar does the same with its bright colors and mood-engaging music. A Little Snow Fairy Sugar is an all-year-round treat to watch, but it is great for the holidays as well. Perfect for the anime-loving family but wholesome enough for an individual. read more 

They're both magical girl anime. =D 

Different settings and different pathways, both shows talk about apprentices growing to become fully fledged in their area of expertise. Both shows are aimed towards children and so are very cute and fun to watch as you see how they grow with each episode. Both do have their moments of drama at times but only so that the characters can grow but all in all very heart-warming to watch. Both shows also have Kotono Mitsuishi playing as an older sister-like figure, although appears more in Usagi compared to Sugar. 

The cities these stories take place in are modeled to a lesser (Ef, also parts of Heidelberg are used) or greater (Chicchana Yukitsukai Sugar) extent after Rothenburg ob der Tauber in Germany. 

both of them are about cute girls doing cute stuff in an idyllic small town, and both main characters work in a cafe 

Both series have the same character designer, Koge-Donbo* Since she's the one responsible for the adorable chibi designs in both anime, if you are a fan of one visually you will be a fan of the other also. 

Fairies, magic, and fairies. Also, both are shoujo animes. 

"Sugar" has a cute protagonist who is somewhat of a brat. This series is A LOT less Otaku-oriented than "Potemayo" and is one of the very few Anime series out there that is appropriate for any age. In other words, it's very much like a G-Rated movie.  

It's made by the same person(Koge Donbo) and both anime has a similar plot: a magical being who trains hard to become a full-fledged magical being. 

Both of these series are shoujo anime about one girl who is one of rare people who can see someone no one else can see.