I don't drink instant coffee on Shabbos.

And neither should you. I won't judge you for drinking instant coffee, but in my opinion, cold brewed coffee is a better option. By simply soaking grounds in cold water for hours and filtering with a permanent filter, one can easily produce coffee that can be kept in the refrigerator over Shabbos. The concentrated coffee can then be used to make iced coffee, or, much like instant coffee or tea essence, can be mixed with hot water and milk. In my opinion, it tastes much better than instant coffee.

(I am very much against coffee snobbery; I believe that a person who insists on drinking only the best coffee is simply unskilled at enjoying lower quality coffee. However, better coffee is still better than worse coffee, even if the worse coffee is also acceptable.)