Hello Alison (also @Burcu) 13:36 Mar 8, 2017
Unfortunately, I cannot comment on any answers, since the asker did not remove the checkmark for proz.com membership. I'd only like to add that I disagree with the "nibbler" suggestion like Edith does. "to nibble" is "knabbern" in German. While I agree with the part about the "diminutive," I can't see Naschkatze or Naschkätzchen being used for anyone not eating sweets. You call this one a "Knabberfreund." So you're right to retain "sugar" as part of the compound noun. | 
peer agreement (net): +8