"저는 식사로 물만 마십니다."
Translation:I just drink water as a meal.
I don't know if you still need it but... The 만 means "only". It's a particle that can change the whole sentence if you attach it to different words. Like : 저는 아침에 커피만 마셔요 (I only drink coffee in the morning ; meaning I don't drink anything else) 저는 아침에만 커피를 마셔요 (I only drink coffee in the morning ; meaning I don't drink coffee at lunch or at dinner for example) 저만 아침에 커피를 마셔요 (I only drink coffee in the morning ; meaning I am the only one drinking coffee in the morning) Hope you understant ^^ (+ sorry for the mistakes (if there are any) in korean and in english, because both of them aren't my native language =D )