A shower requires specific materials to be recycled so that players can repurpose them. At the beginning of the game, it is unlikely to have these materials straight off the bat, so inevitably your bunker dwellers are going to get a little... funky smelling. The best way to deal with this is to have them stand topside In The Rain.
When they are stood out in the open when it is raining, their shower need will naturally fill back up, meaning you can get by without a shower in the bunker for a little while. It isn't the most convenient as it doesn't rain every day, but it's the way to work around being showerless before you have the right resources.
Having a shower in nature will do the trick for a little while, but it will not last as long as having a shower with soap. It is better than nothing, though, and will make your survivors a little happier until the next downpour!
Have fun getting clean au natural! Looking for more content? Why not check out how long food poisoning lasts in Sheltered 2?
