Final answer:
The provided references do not mention Bruno's fondest memory of his grandmother from 'The Boy in the Striped Pajamas'. Typically, such fond memories revolve around personal and meaningful activities which could range from baking together, storytelling, receiving gifts, to sharing laughter.
Step-by-step explanation:
Bruno's fondest memory of his grandmother in The Boy in the Striped Pajamas is not directly mentioned in the provided references, so it is important to be familiar with the text itself to provide an accurate answer. However, based on common themes of grandparent-grandchild relationships, it's plausible that his fondest memories might involve a personal and emotionally significant activity such as baking cookies, listening to family stories, receiving presents, or sharing laughter during family gatherings, as hinted at by the examples given in the reference material. To provide a precise response, one would need to refer to the specific events and interactions detailed in the novel between Bruno and his grandmother.