。
I could hardly eat rice during the trip.
Literal
Trip-during [topic-は] almost rice [topic-は] couldn't-eat.
ほとんど + negative = 'hardly/almost not at all.' 食べられなかった is the potential negative past of 食べる — 'couldn't eat.' The contrastive は after 米 implies 'as for rice specifically, I couldn't eat it' — possibly because of being in a non-rice-eating country. A culturally relatable observation for Japanese travelers abroad.