wine and sparkling water
The simple Spritzer—a bit like a wine sling or highball—began in Austro-Hungary as a way to lengthen and lighten the local wines into something more like beer, for easier, more refreshing drinking. This practice remained popular in northern Italy after reunification, and there, in the early twentieth century, variations incorporating vermouths and amari emerged. Two important examples of these variations are the Americano and Aperol Spritz. The spritzer also remains popular in Austria to this day, and the “wine cooler” that was common in the USA in the 1980s can be viewed as a (degenerate) commercial variation.
A spritzer is, first, about the selection of wine, and second, the proportion of wine to sparkling water (or in some cases, a carbonated soda or fermented apple juice). The wine is almost always a white wine. Proportion can run the gamut from low to high. Any syrups, liqueurs or other additions are up to you. The possibilities are limitless, and everything depends upon the situation and your good taste. Working with well-chilled ingredients rather than building over ice will preserve the carbonation best.
Oxford Companion to Spirits and Cocktails, p. 28–9; barware icons courtesy of Haus Alpenz