Answer
In themselves, they have no connection with the quality of chanting, provided they are prasadam. Whether you take cake, sweet rice, or ice cream offered to Krishna, they do not inherently obstruct chanting.
However, overindulgence can affect the body and mind. If you eat excessively—such as consuming a large quantity of sweet rice—your body becomes disturbed, and the mind becomes less steady. An unsteady mind makes it difficult to concentrate on the holy name.
The real secret of chanting is hearing. Krishna is present in His holy name. The essential instruction is:
Do: Hear.
Do not: Think unnecessarily.
Hear the holy name again and again. Continue hearing attentively. This hearing carries tremendous spiritual power. It is a direct connection with Krishna and acts as a spiritual shortcut.
By sincerely chanting and hearing, one gradually gains spiritual knowledge, inner strength, and control over the tongue and the senses. The many subsidiary rules and regulations of spiritual life become easier to follow naturally.
The most important principle is to chant and hear attentively, especially one’s prescribed rounds of japa. If that is taken care of properly, many other aspects of spiritual life become automatically regulated.