upsells(多卖一些)

A sales strategy where the seller will provide opportunities to purchase related products or services, often for the sole purpose of making a larger sale. A popular example of upselling happens when a fast-food customer orders a hamburger, and they are asked by their cashier “Do you want fries with that?”, in an attempt to get them to purchase more food. Other examples of products that are upsold are warranties on electronics purchases, and the purchase of a carwash after you purchased gas at the gas station.

快餐店顾客买了汉堡，收银员会问还要不要炸薯条

cross-sells(卖一些其他的东西)

Encouraging a customer who buys a product (gasoline, for example) to buy a related or complementary product (engine oil, for example). Cross-selling is generally illegal if there is a tie-in between the two products; where the customer must buy one in order to buy the other.

在加油站问买了汽油的顾客要不要买机油