What does he mean by "rustle up some grub"?

Native speaker’s answer
Rebecca
Great question! To "rustle up some grub" means to prepare (look for/make) some food or a meal! A slang word for food is "grub," and "rustle up" means "to prepare." Ex: I'm going to rustle up some grub for you. Will be ready in twenty minutes. Ex: The burger shop near my house has some good grub.