Which of the following can be used as a substitute for soap in cleaning glasses?

Soda water is an effective substitute for soap when cleaning glasses due to its effervescence and mild acidity. The carbonation in soda water aids in lifting dirt and grime from the surfaces of the glass. Additionally, it can help remove odors, making it a good cleaning agent for glassware, particularly in bartending where cleanliness is crucial for appearance and hygiene.

Using soda water is also safe for cleaning glass, as it doesn't leave any harmful residues or strong scents that might interfere with the taste of beverages served in these glasses. This is especially important in a bar setting, where glasses may be used to serve drinks immediately after cleaning.

Other options, while useful in some cleaning contexts, may not be as effective or safe for cleaning glasses specifically, which is why soda water is the preferred choice.