What's the best way to show my appreciation for my junior enlisted?

First off it is obvious you're ahead of the curve just by posting this question.

While I do not have the leadership experience you do I can say this:
Everyone wants to feel important. (Give a high priority tasker)
Everyone wants to feel appreciated. (Hearing "Great Job or "Thank you!" goes miles)
Everyone wants to be recognized. (Positive counselings, Letters of Commendation, etc)

If you are busting your hump to make sure your Soldiers promote, receive deserved awards, are given opportunities to advance their training, have maximum liberty without hindering the mission, and have the ability to approach you about anything, then you have nothing to worry about. If we had more leaders that were willing to see their juniors as more than just subordinates we would be a much more efficient military.

- Doc

It's the unexpected that counts. A cooler full of ice cream on a hot day coming back from a ball buster. Pool time on a hot day. I'm OK with the BBQ mentioned by another member but they tend to be more planned and can taint of "command performance". Everything in moderation. PRCA rodeo comes around, go for it. The list is endless. Don't forget, a community project with a meal afterwards breaks up the routine. Most SMs just want to be acknowledged as there and as humans. Treat everyone as much more than that.

Do your soldiers come to you for advice, do they greet you cheerfully and take time to check with you at the close of day? Do you feel a sense of espriit de corps with the platoon? If these kinds of things are happening, then you have already earned their respect as a leader.

I think just gathering them together informally and letting them know that you appreciate them is enough.

Just continue to have their backs and you will continue to show them that they are valuable