Owner suggests extra items to guests in two places: at checkout, and in the Goes Well With section on an item. You can influence checkout suggestions. Goes Well With is built from your orders.
Requirements
The Manage menus permission. See Staff jobs and permissions.
Know the two kinds of suggestions
Checkout suggestions: items suggested in the cart and at checkout. Upsell Item and Upsell Categories make items more likely to show here.
Goes Well With: a section on an item's page. Owner builds it from what guests order together, and you can't pick which items show.
In the Owner Dashboard
Suggest an item at checkout
Open Menu › Items, then select the item.
In Promotion, turn on Upsell Item.
Click Save Item.
Only items with a photo can be suggested at checkout. Upsell Item makes an item more likely to show, but doesn't guarantee it.
Suggest items from another category
Use Upsell Categories to suggest items from one category when guests order from another. For example, suggest drinks when guests order a burger.
Open Menu › Categories, then select the category guests order from, such as Burgers.
In Upsell Categories, choose the categories to suggest, such as Drinks.
Click Save Category.
How Goes Well With works
Owner chooses these items mostly from what guests order and add to their carts together, and from each guest's past orders. Price matters a little. Upsell Categories has a very small effect, and Upsell Item has none.
Only items guests can add in one tap show here. Items with option groups don't.
Suggestions change over time as you get more orders, not right after you change a setting.
You can't choose or remove specific items.
Check what guests see
On your ordering website, add an item to your cart and go to checkout. Check which items are suggested, without placing the order.