For 2 adults and 1 kid (and we all bike at least several km daily), we had:
scrambled eggs with sautéed mushrooms, avocado, and toast. And the kid had a few large cherry tomatoes as she doesn't care much for mushrooms. There were no leftovers.
All ingredients are prorated as we'll eat the remaining ones in the future. My husband also had a beer, which costs about 1€
eggs, 0.80€
scallions, 0.20€
garlic, 0.10€ (maybe? I used a couple of cloves)
oil, 0.05-0.10€
toast, 0.20€
avocado, 1.00€
tomatoes, 0.30€
total: 2.70€