There is no special characters token for normal spaces, as you would usually simply use a normal space to denote a space.
However, in some cases you might need to specify that a character is a normal space (ie. not a non-breaking space), but that for sorting purposes, it should be ignored.
For example, in the saints and namedays manager, you can use a tilde (~) to specify where a normal space should be inserted during diary generation, but that for sorting purposes, such as in the saints/namedays options, words separated by a tilde are to be treated as a single word, so that they should not be broken-up in the process of sorting.
See also: non-breaking space.