Pear

Pears were a type of fruit.

When the Seventh Doctor turned himself into John Smith, he left instructions for Bernice Summerfield, one of which was to not let him eat pears, as he didn't like them and didn't want to wake up tasting that. (PROSE: Human Nature)

After the Tenth Doctor turned himself into John Smith, he could be seen eating a pear as he wandered near his fob watch. (TV: Human Nature)

Behind the scenes
In a deleted scene from TV: Human Nature, when the Tenth Doctor turned himself into John Smith, he left instructions for Martha Jones, one of which was to not let him eat pears, as he didn't like them and didn't want to wake up tasting that.