How long can a teen survive on the contents of a Ryanair size carry bag (40cm x 20cm x 25cm)

[CellarCaller]

My son is planning to go abroad for the first time in the summer for 5 days and will only have a carry on bag as described.
Can you fit enough in such a bag?
It's in Germany so temperature will be similar to southern England in late August, early September.
Thanks

He'll be fine - my DS does it all the time. He goes away four or five times a year for a few days at a time, never takes more than the smallest Ryanair carry on. He bought a bag that was the absolutely maximum dimensions, rolls his clothes to pack, wears anything bulky. He usually wears jeans, tshirt, hoodie, perhaps a coat depending where he's going. Then packs a couple of t-shirts, a pair of shorts/trackies, underwear, deodorant and toothpaste, flannel, and he's good to go. He just washes anything through with soap/shower gel that he needs to when he's there.