Review the original item:
Neil's day revolves around sugar,
he anticipates the pastry that he will choose for breakfast, the
candy bar that he will eat for lunch, and the ice cream that he will have
as dinner.
You wanted to fix it this way:
Neil's day revolves around sugar,
but he anticipates the pastry that he will choose for breakfast,
the candy bar that he will eat for lunch, and the ice cream that he will
have as dinner.
A good way to fix a comma splice is to add a coordinating conjunction like but. When you use this method, however, you must choose a coordinating conjunction that logically connects the two main clauses.
In the example above, but is an illogical choice because the sentence is not showing contrast.
You might want to consult the rules for fixing comma splices and fused sentences.