What does the word soda mean?

Usage examples for soda

  1. He flung his hat on the sofa, and opened the window and door, so as to let in the cool breeze; then mixing for himself a glass of brandy and soda, he turned up the lamp, and prepared to read his letters. – The Mystery of a Hansom Cab by Fergus Hume
  2. I mixed him a sleeping draught with his whisky and soda. – The Great Impersonation by E. Phillips Oppenheim