This was sold to us as as a sudachi, but in the photos I see online the fruits are larger (these are about 1") and dark green so I think this is something else. Also, sudachi are not a Clementine-tangelo hybrid.
The flavor is unpleasant, I can’t really see any culinary use unless maybe the fruit isn’t ripe yet.
https://citrusvariety.ucr.edu/citrus/sudachi1.html
It shouldn’t be sweet, in Japan it’s used as a souring agent for broth or for ponzu. I’ve been told by a farmer that because of climate differences between here and Japan they turn color sooner. Haven’t verified this myself.
Yeah, sudachi should be sour, but if this is not a sudachi, maybe they’ll eventually ripen and turn sweet.
A citrus grower friend suggested I wait until the fruit starts falling off and then pick one from the tree.
Yuzu / lime / lemon / orange tree owner here. Lawd I wish I could grow sudachi here in SoCal (but as many Japanese have told me, it’s just too damn hot here). That does not look like a sudachi tree. My reasons for saying so is the fruit size looks off. As for color: Most all citrus will turn yellow (yuzu, limes) if one lets it sit on the tree long enough without harvesting it. Some non-orange citruses might even turn the color orange if it stays on the tree long enough.
Interesting tidbit: Limes, IMHO, taste so, so much better (perhaps more sublime? 
) after tree-ripening the fruit and harvesting it only after the lime turns yellow. The problem is that yellow-colored limes look pretty much exactly like lemons, and so they’d confuse the hell out of inventory control at the greengrocer level. The resulting fallacy is that the public believes green limes are best.
Thus, like many citrus fruits we use for primarily for fragrance and zest (yuzu, sudachi, etc.), limes too are harvested early, when they are still green. Some local Japanese Chefs I know ask me to supply them young yuzu (green), as there is a special flavor to their zest to be found during that time, and also because most commercial yuzu outfits refuse to harvest fruits early.
