Is sweet sweet sweet a repetition?

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 sings of the woman's 'cold cold heart' and Robert Burns' poem "My Luv's like a red red rose" repeats the Word red for effect.