What are some side hustles I can do while in the Army?

(1) Start building a portfolio for your passions in Media Design and Photography:

-- make a simple landing page that points to your Twitter, Instagram, etc.

(2) Start building an audience for your works and your voice

-- commit yourself to post regularly on these platforms (can be your works or just something of value like photography tips, howto, etc.)

-- write to companies to offer to do projects for them (photography, etc.?)

(3) Take time to pick up other skills too (programming, coding, UX/UI design, etc.)

-- you may find an interesting niche for yourself with your media design background

(4) Read, read and read more

-- this will help you level up very quickly in so many areas

Nowadays, you can try to look into social media profession, helping to build someone's social media portfolio. It would be a good stepping stone for yourself as social media is going to be the new-generation of work-life and it would be good money as well.