Put one of the drinks in each cup and label all of them with masking tape.
Store the cups where they will not be disturbed.
Wait a few hours or overnight.
Science Behind It
Eggs are protected by a calcium carbonate shell. Calcium carbonate is the same thing that our bones and the enamel on teeth are made of. Sugars and acids, like the ones in sodas and juices, harm the calcium carbonate. The acid reacts with the calcium carbonate and produces a compound that dissolves in water and carbon dioxide gas, which eventually dissolves the egg shell.
Tips
This would be a good project to start at the beginning of a meeting and finish at the end, or for a two-day meeting.