Yes, you can add foods to a meal plan without creating or using recipes.
To do that, open a meal plan or create a new one then click on the Plus button and choose "Add Food" instead of "Add Recipe". From there, you can search for the food or ingredient that you want to add and select it. You can add up to 10 foods in a single meal type.
This makes it very easy to create food plans where you just select the foods your clients should eat and give them the freedom to make their own meals.