At a Pidyon HaBen I have observed that the Minhag is to put sugar cubes and garlic cloves on the tray with the baby. What is the source of this Minhag? And why specifically sugar and garlic?
According to this it's because garlic and sugar are spices which last along time and get put in multiple dishes. This way, people can take some of the garlic and sugar home and thereby be able to partake in the mitzvah-food for a long time to come. A similar idea can be found here.
According to this it's because sugar shows that mitzvot are sweet and garlic is a symbol for fertility.