Those items are "buy one get one free".

这些东西都是“买一送一”。

youdao

We're having a buy one get one free sale today.

我们今天有买一送一的优惠哦。

youdao

In the land of plenty, we are constantly tempted with more ways to spend: bigger servings, buy one get one free offers, and endless opportunities to get rich quick.

在富饶之地，有太多种不断引诱我们花销的方式：丰盛的餐饮、买一送一、无数的快速致富机会。

youdao

The firm said the offer meant that smaller households would not be forced to throw out "buy one, get one free" items before their use-by date.

BBC: Tesco launches Buy One Now, Get One Free... Later

Heck, offer me a BOGO (buy one get one free).

FORBES: Why Americans Should Go Postal Over The Postal Service Default

The idea is to strip away the complexities of buy one get one free deals and other special offers and find out which supermarket really offers the best value.

BBC: Week ahead