Minimal Pairs are words that sound very similar but are still different.
Fluent Forever (
https://blog.fluent-forever.com) for example, is a strong advocate for it.
Here in Mandarin, I assume that the "similar sounding" words are words with same Pinyin but different tones.
I scrapped all the words of HSK, from level 1 to level 6.
Each card has a few words (from 2 to 4) and an audio. The goal is determine which word belong to the audio.
Note that for this deck, your native language doesn't matter. The only goal is to distinguish the audio.
The audio was generated mainly with Forvo (a real-voice database) but a few were generated by Amazon Polly's Zhiyu (the one used by Duolingo).
Happy learning!