I don't use Reddit actively anymore (just when a link leads me to the site) but the last time used it actively and even today when I have to access the site on mobile my favourite app is Reddit Is Fun.[1]
Its free version[2] is as good. I just bought paid one[2] to support the fantastic app. They also have the source code of an old version[4] available online, though the app's current source is not open sourced I think.