PS I looked at Burrascano and he is thorough on the topic -- he says fruit is all right in moderation, but not on an empty stomach -- only after a meal.
Probiotics are important to take when on antibiotics to replenish the 'good' bacteria that are killed off along with the 'bad' bacteria, and I am assuming your LLMD has you on probiotics, perhaps Florastor, which is yeast-based and therefore not wiped out by antibiotics. Some people (like me) get colonized by the yeast, but I understand that is a rare reaction.
More likely is getting a serious and potentially life-threatening bacterial infection (esp. C. difficile) when other 'good' bacteria are wiped out of your gut by antibiotics. C. difficile is not wiped out by regular antibiotics and responds only to certain specialized antiobiotics that are not commonly prescribed; therefore avoiding C. difficile infection is important, and the usual way to do that is to take something like Florastor, or potentially non-yeast-based probiotics at times separated from the time you take your antibiotics.
Your doc will have guidance on this point.
I have not read that sugar feeds Lyme bacteria directly, but when taking antibiotics, yeast can get out of control because the abx kill the good bacteria too, which would otherwise keep the yeast under control. At ILADS dot org, Burrascano's treatment guidelines discusses approaches to yeast control.
If you are craving chocolate, it could be the B vitamins that you are responding to, dunno. There is unsweetened powdered chocolate available in the grocery store that is pretty good sprinkled over bananas ... but bananas are high sugar and so feed any yeast problem. See what Burrascano has to say.
I got bad brain fog and bloated gut -- and I mean really bloated -- when I had a very bad systemic yeast infection. A bunch of MDs missed the diagnosis, so you have to watch out for yourself.
Lyme does odd things to body metabolism, and when you add in antibiotics and are not taking probiotics, it can lead to problems. Read Burrascano. He's pretty detailed on the topic.