Cucumbers are a vegetable. How can they not be essential? It is food, a vegetable with a lot of nutrients.
Anyway, what has essential even got to do with food purchases? If you need to go shopping for something, you're already in the store, so what law says you can't buy ice cream, for example? If you did 2 trips, one for ice cream solely, yes, that would be unreasonable. But if you are already there, then does it matter? Why does it matter what one buys? If you're there in the store because you needed food (whether bread, milk, vegetables etc), you're there anyway, so why can't you add what you want to your shopping trolley? I am genuinely confused that people think you can't buy 'non-essentials' when one is already in the store anyway. Coke, ice cream, biscuits, alcohol, who cares? It never was about essential 'food'.
It's about non-essential TRIPS. Not non-essential purchases. Nowhere is food items even mentioned. Where the heck did this come from???