This app was mentioned in 2 comments, with an average of 1.50 upvotes
GetKana
https://play.google.com/store/apps/details?id=com.getkana.app
Simple app without unnecessary ballast or distractions. Multiple choice (1 of 4), endlessly repeatable. With a good tablet or phone you can answer about one question per second, fast enough to bring you close to an acceptable reading speed for actual texts. Any number of consonant groups (eg まみむめも) can be activated for the practice session.
I use this https://play.google.com/store/apps/details?id=com.getkana.app
You can pick what to learn, what not to learn, and what unlocks automatically later on.
Pretty straightforward