This activity is great for students who constantly mix up similar looking notes.
The teacher chooses which two notes the student needs to work on, and writes the letter names on the lemon wedges. She then gives the student "ice cubes" with the corresponding notes on them. The student has to match each note to the correct glass of lemonade.
This PDF includes 6 sets of commonly mixed up notes. All in Middle C position:
Middle C & E
Middle C & A
A & E
D & B
F & G
G & F