We need to know the time you are asking about. Soldiers throughout time have eaten in various ways using various methods.
What do the Roman Soldiers eat?
They stopped by houses on the way and took all their food
Hardtack
See the question: What did the soldiers in World War 2 eat?
They have to eat what they can find on the land where they fight.
What do the Roman Soldiers eat?
Time Soldiers was created in 1987.
Time Soldiers happened in 1987.
Hardtack
worms
They eat human food