Cook milk in a small nonaluminum saucepan over medium-low heat, stirring once, 2 to 3 minutes or just until bubbles appear (do not boil); remove from heat. Add tea bags; cover and steep 5 minutes. Remove and discard tea bags from milk, squeezing gently.
Stir together granulated sugar, cinnamon, and flour in a large bowl. Cut in butter with a pastry blender or a fork until crumbly. Add 3/4 cup milk mixture, stirring just until dry ingredients are moistened. Reserve remaining milk mixture for later use.
Turn dough out onto a lightly floured surface; knead lightly 4 to 5 times with floured hands. Pat dough to 3/4-inch thickness; cut with a 1 1/2-inch round cutter. Place on a lightly greased baking sheet.
Bake at 400° for 6 to 7 minutes or until golden. Let stand 5 minutes. Whisk together reserved 1 Tbsp. milk mixture and powdered sugar until smooth. Drizzle over warm biscuits.