This carbonated water DIY reminded me of fröccs, or spritzer as the German say, and how apparently they mention it in English, although splash would be a good translation.
As far as the story goes, it was invented in the early 1840s, and it's just a simple mix of wine and carbonated water. In theory all types of wines can be used, I think only authentic with white wine. If there is a ratio it can be mixed together they do it, but from my childhood, I only remember three which was used in the talponállós (literally means: stand-on-your-soles, it's a type of pub for the proles where no seats can be found, chairs or barstools of any, and the tables are all chest height, so one can only stand next to them; it's a place where factory workers could drink before and after their shift):
- small fröccs, wine and carbonated water 1 dl each
- large fröccs, 2 dl wine 1 dl carbonated water
- long step fröccs, 1 dl wine, 2 dl carbonated water.