Suggestions can be set up as default for the entire category, or for individual items.
In this example, we will create a suggestion for garlic bread or breadsticks when a pizza is ordered.
Configuration > Items > Pizza > Specialty Pizza > Edit
You will be taken to the category edit screen > Click Suggestions on the sub-navigation menu.
Find the items you wish to add to the suggestion popup on the left side of the screen (Suggestions Setup) and add it to the right by clicking the double arrows.
Block this Category From Being Suggested: If checked, this category will never appear in a system-generated suggestion such as "other customers ordered this".
Move Up/Move Down: Prioritize the items in the order you wish them to be suggested. Customers will see only one suggestion per item ordered; Items already on the order will be skipped.
Save your changes.