How do you do sweet?

I'd say it is. Repetition is something (an idea, a word, a phrase etc. etc.) which is REPEATED for effect. Here, the word 'sweet' is repeated. It is done for effect. Hank Williams in one of his songs...

The sweet potato has natural sugars in it that makes it sweet to the taste.

Sweet Tarts are a little bit of both. It tastes more sour but it is really equal.

yeah they are!

Sweet potatoes are not actually sweet. They are called sweet potatoes because they are not bland, and people back in the day had never tasted such a good potato before. Because they considered candy...