Most Sona’s will run through their mana incredibly quickly through poking and providing heals. Capitalize on this by looking to fight her when she has no mana available.
Sona is incredibly vulnerable in the early game. Before level 6, try to abuse her as much as possible. Once she is level 6, her kill pressure increases as her Ultimate R is a great duelling tool and has great gank set up too.
The best time to play aggressively is when Sona overextends to get stacks on her Spellthief’s Edge. When she is overextended, try to play aggressive and burst her down when she’s positioned forward.
Catching Sona out when she goes to ward will allow your team to potentially allow you to take the Baron, Dragon or start a team fight when she is unable to protect her team.
Avoid team fighting in areas where you’re forced to group close together like inside an objective pit or in the jungle. This will allow Sona to get a multiperson Ultimate R. Try and group but not too close together.
In team fights, Sona will be stood next to her ADC. This might make it difficult for you to kill her. Not to worry, you could flank in team fights to make killing her or her ADC easier.
Once Sona hits level 6, her kill pressure increases and she can start to play more aggressive. Additionally, her Ultimate R offers her extra gank setup, so expect her Jungler to gank post 6.
Sona’s healing from her W will be a problem as the game goes along. Make sure your team invests in Executioner’s Calling to reduce her healing ability.
The more gold Sona gets-, the more of a problem she will be. Try to set her behind to delay her crucial item spikes.