Oatmeal

OP didn't actually mention packets, and you can buy instant that's just oats.

One example: https://www.mymccanns.com/product_categories/instant-irish-oats/

Nutrition facts in the plain instant: 28 g, 100 cal, 3 g fiber, 4 g protein.

For the regular: 40 g, 150 cal, 4 g fiber, 4 g protein -- looks like the same but slightly off due to different sizes and rounding.

A different brand (Bob's Red Mill, plain, not quick cook):

44 g, 170 cal, 4 g fiber, 4 g protein

And their version that comes in a microwaveable cup:

51 g, 200 cal, 6 g fiber, 7 g protein.

All of the above is just oats.

Given that OP mentioned adding cinnamon, I assume the oats in question are just oats, but the idea that adding some other ingredients to the oats (all of the above come with some flavored options) is inherently bad is odd. Sure, in some cases they may be adding more sugar or other ingredients you don't want (which does not eliminate the benefit of the oats, that's silly), but in other cases the ingredients added might be similar to what you'd add yourself and still allow for carry and eat on the go. (Oh, and personally lots of store-bought almond milk includes ingredients I avoid. I don't therefore write a post telling you never to consume almond milk.)

I never eat instant oats, so this is not a personal thing, I just dislike inaccurate and fear-mongering information. How I make non instant thicker is to control the amount of water added, or use a mix of milk and water, but that might be harder to do with instant. I also sometimes add cauliflower, as mentioned above, or seeds or chopped up apples with cinnamon -- the apples soak up some of the water. Peanut powder makes them thicker too.