In Basic Combat Training they eat in a dining hall and are served hot meals when they are in their company area. When doing field training part of their learning is dining on combat rations. On extended field problems a field kitchen will be estabilished and feed the troops.
Soldiers are persons who have completed Basic Combat Training. They are assigned to a Unit that has a reason (mission) other than Basic Training. They do train though to complete their assigned missions. Troops in the field will eat combat rations on some of these problems. But their training also includes the people who have the mission of feeding the troops, so a field kitchen will be established to serve troops hot meals.
The Army got rid of the "trainee/soldier" thing a long time ago. Now, you're a soldier the minute you're sworn in. (The Marines still hold that a person is a Recruit until he's graduated from Boot Camp and earned the title United States Marine, but that's Uncle Sam's Misguided Children for ya.)
Anyway, there are a lot of different kinds of military training. A lot of it is classroom training, and you eat in a dining facility, which is kind of like a restaurant. The sergeant that runs it has a great deal of latitude as to what he serves, so you could conceivably eat anything in a dining facility. I was in a unit where the food service sergeant loved roast lamb and served it every Wednesday to a packed house.
If the soldiers are doing field training, there are many ways to feed them. One popular method uses "mermites"--insulated containers to carry food from the mess hall's kitchen to the soldiers in the field. They just cook the stuff in the rear and truck it out. There are Mobile Kitchen Trailers, which are just what they sound like. They've got the Army Field Feeding System, which relies on "T-rats"--sealed metal trays holding enough of a dish for twelve people--and Meals, Ready to Eat. The AFFS isn't used all that often during training because it's very expensive and food service sergeants don't like to spend the money. There are Wolfburger stands, which are kinda like concession stands at carnivals.