Prepare brownie mix according to package directions, using 1/4 cup cherry juice plus water needed to equal amount of water called for in directions. Place paper liners in mini muffin cups; fill about 1/2 full of brownie batter. Push a cherry into each cup; bake at 350° for 15 to 20 minutes. Remove baked cups in liners from muffin cups; let cool.
Combine chocolate chips and condensed milk in a small saucepan; stir over low heat until melted. Remove from heat; stir in remaining 1/4 cup cherry juice as needed for frosting consistency. Place a dollop of warm frosting on each cherry cup; let cool.