How to counter Sona
Let us take a look on how to beat Sona. We will look at champions who are strong against Sona and who are weak against Sona. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Support champion who counters Sona. You can already win in champion select with the right counters for Sona. If you want to know how to counter Sona then you need to take into account the best picks vs Sona and the worst picks vs Sona. This Sona counter data is based on matches played by Pros on patch 13.21 and previous ones. It is important to see whether Pros counter picked Sona or whether they played as Sona.
Champions used by Pros to counter pick Sona
Looking at the matches from Pros (see table Pros counter picked Sona) we can see that they picked 
Rakan most often to counter pick Sona. The matchup Rakan vs Sona occured 19 times. Sona has 8 wins and 11 losses in this matchup. Learn how to counter pick Rakan to get another perspective on the data.
Lane outcome for Sona
When looking at Sona counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Sona. The lane outcome of Sona consists of three outcomes: Win, Loss or Draw. Let's take a look of Sona lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Sona.
Conclusion
Analyze the available data and learn how to beat Sona. To master Sona take also a look on Sona builds and runes for Sona. Good luck, Summoner!