There are at least three literary devices present. Both of the examples in the title, "asparagus to avocados" and "kangaroos to koalas" exhibit two of them. Those two devices are alliteration, and juxtaposition. Alliteration is the device where two or more nearby words begin with the same, or nearly the same sound. In the case of the vegetables, the sound is "a"; in the case of Australian fauna, the sound is "k". Alliteration is the opposite of rhyme, the literary device where two words end with the same sound.
Juxtaposition is the literary device which puts uses two items in side by side placement to bring attention to some particular concept or idea. In the case of the asparagus and avocados, the idea might be to bring attention to the breadth of offerings in a produce department. In the case of the 'roos and koalas, it is to call attention to the diversity of the fauna of the Australian continent.
The combination of alliteration and juxtaposition is likely influenced by marketing considerations. Alliteration is sufficiently rare in common English speech and writing so as to be more memorable when it is noticed, so more people are likely to notice and to remember "asparagus to avocados" than are likely to notice and remember "avocados to tomatoes", and similarly "kangaroos to koalas" will be noticed and be remembered longer than "dingos to wallabys".
There is a third literary device at play in the first example, "asparagus to avocados", as well, assonance, which is when two words in close proximity each include the same, or very similar vowel sounds, in this case the sound of the initial "a". However, unlike alliteration, assonance is not limited to the initial sound of the word, nor to the same position in the word. "Avocado with cod (fish)" and "periwinkle twinkie" both are examples of assonance.