Bring four cups water to a bowl in a teapot or saucepan. Remove from heat and add tea bags. Allow tea bags to steep for several minutes.
Prepare infused simple syrup: combine ¼ cup water, honey, lemongrass, and cinnamon sticks in a small saucepan and place over medium heat. Simmer, stirring occasionally, until mixture starts to thicken, about 4-5 minutes.
Remove from heat and pour through a fine mesh strainer to separate the solids from the liquid. Discard solids and set the remaining simple syrup aside to cool.
Combine the brewed tea, lemon juice, and remaining cup of water in a large pitcher. Add infused simple syrup, to taste, and stir to combine.
To serve, fill chilled glasses with ice then add the sweetened tea mixture. Add garnish (optional) and serve.