Here's a reading text with comprehension questions on healthy food. It covers the vocabulary set of healthy and unhealthy food. It's a conversation between a storekeeper, who doesn't sell unhealthy food, and a customer who wants to buy unhealthy food!
There's also the video of this conversation. You can watch it before giving the comprehension questions. The link is also given in the QR code.
If you like to extend your reading lesson, here's the second part of this reading.