Lubricant for spontaneous sex between two men in a shower?

My setting is futuristic-military: earth-born soldiers doing their tour of duty defending fledgling human colonies on other planets against aliens.

I have two soldiers who have been attracted to each other for a while, alone in the barracks showers. Sex ensues. My question is: what can they use as a lubricant?

I found that water is no good, soap is no good. Is there anything else that could be used? (For any site that recommended anything, I found two that said never to use that same thing. It left me very confused.) I should add they are not using a condom (vaccines for STDs instead). Is there any chance at all that with no condom, they wouldn't need a lubricant for anal/have options that are incompatible with condoms?

Considering the sex is based on a combination of attraction, needing to feel alive after the horror of a combat situation, and post-combat "life is too short to keep on being shy", I feel that frottage would be too intimate for the characters. Are there options other than anal that are not face-to-face, and would work with the absence of proper lubricants?

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I second taking advantage of the futuristic setting but I’m mostly commenting to say don’t feel put off by the comment above. Firstly, I’m sure if people can suspend their disbelief for everything else futuristic then they can believe in “this future thing doubles up as lube”. Secondly, from the sounds of it, this scene has meaning and is part of the character/relationship development and if your question was about any other plot point, nobody would be telling you to just vague over it. Lastly, even if it wasn’t a plot point, please don’t let them make you feel like you shouldn’t write what you want to write, whether they find it tasteful or not.

Also, there’s also intergluteal, if you want to do something different to penetration while keeping it less personal.