Sentence:  About how long has it been since you last bought <WSD>tomato juice</WSD>? ... About how often do you buy <WSD>tomato juice</WSD>? About how many cans do you buy at a time? ... 
Meaning of the word marked with <WSD> tags:  Juice made from tomatoes. In modern use, this usually refers to the comminuted flesh and juice of cooked tomatoes, prepared commercially.