Hi,
I just feed a decent kibble or tinned food on a journey. Kibble‘s easier really, especially if you‘re in a hotel or whatever, you don‘t have the problem of washing out bowls and its just a lot less messy. I tend to just give Humphrey a tiny amount every now and again when we stop, it stops him getting too hungry but also doesn‘t overload his tummy. Obviously every dog is different, but that‘s always worked for us.
I don‘t think it does any harm now and again, - we also have to compromise foodwise on a longer journey, and trying to stick to raw diet while travelling is tricky.
Enjoy your trip!