Brew a strong batch of black tea and let it cool completely to avoid melting the ice too quickly.
Pour the cooled tea into a blender and add sweetener, like sugar or honey, adjusting to your desired level of sweetness.
Add the ice cubes to the blender, filling it up to about three-quarters full to ensure a thick, icy texture.
Blend the mixture on high speed until the ice is fully crushed and the texture is smooth and frosty, about 30-60 seconds.
Pause briefly to check the consistency—if it's too thick, add a splash more tea and blend again; if too thin, add extra ice and blend briefly.
Pour the vibrant, icy slushie into glasses and garnish with a slice of lemon or fresh mint if desired for extra visual appeal.