Not for everyone, but if that is you: If you book basic (no checked bag) but even a carry-on (“cabin bag”) costs extra, like A LOT EXTRA, make do with minimal toiletries and undies etc in the “personal item” that goes under the seat, and buy a few extra garments on arrival at the nearest thrift store. The 70 or 80 bucks I’ve seen lately buys you quite a wardrobe! Plus - these often are fun places! Donate back before you go home.
I'm adding this as an edit. I have received pushback this afternoon from folks who do not sound like rockbottom budget travelers. As I said, not for everyone. I'm addressing this to folks who might fly EWR>ORY for $156 (Sep. and Oct. dates on French Bee), or JFK>LGW for $162 or $204 or even $243 (Norse Atlantic), and take other such cheap flights. These airlines restrict the carry-on to 10kg (legacy airlines have no weight limit), and - here's the thing - once you got to Europe on the cheap, you want to keep going on the cheap if you're a rockbottom traveler. You pick the basic fares and you have to pay extra for carry-on, on EasyJet, Norwegian, Pegasus, Ryanair, Volotea, Vueling, Wizz Air... Crisscross Europe and that adds up quickly. So this idea (not an Internet hack) is for folks who stay in $15/night hostels and religious guesthouses, like to immerse themselves, figure out things and use buses etc, and don't mind mingling with locals at a thrift shop to save money. Again, not for everyone. Fair enough?.