Champagne splits are 187ml (1/4 sized bottles), although sometimes half bottles, 375ml, are mistakenly called splits. This is barely one large glass or two small glasses.
Champagne splits are often used as party favors or included in gift baskets and are a favorite at weddings.
Champagne splits are also useful for the few cocktails that need a Champagne in them. An example is "The Champagne Cocktail" which has Champagne, sugar and a dash of bitters. The Champagne Cocktail is one of the oldest known cocktails and sounds pretty horrid to me. A Kir Royale is Champagne with crème de cassis and is pretty good. Of course there is the classic Mimosa: Champagne and orange juice, freshly squeezed please. Other examples of Champagne cocktails include the Dutch Tulip, Elderflower Cocktail, Flirtini, French Pear Martini, Happy New Year, Raspberry Bellini, Tickled Pink, and Vampire Kiss Cocktail. Some of these sound pretty horrible.
Please don't waste great Champagne on Champagne cocktails! A middle of the road Champagne or sparkling wine is usually fine. I usually use Spanish Cava which is one of the great deals in the world of wine.
You won't find much choice of Champagne in splits, although a few decent ones are available including Pommery, Perrier-Jouët, and Nicolas Feuillatte. And of course there are many splits of cheaper Californian sparkling wines and others available, and quite honestly most people don't know the difference, at least among the "split crowd" - for example the folks at Cousin Beatrice's wedding.
Pommery Pop Pink Rose is popular and interesting - it comes with a straw for drinking through. It's designed for people who like the idea of drinking Champagne more than Champagne itself. It's not bad though, although please, ditch the dumbass straw and drink it out of a proper glass or right from the bottle. A suppose drinking it from a woman's shoe is OK too, if you're drunk, she's half your age, you own a yacht, and you're male or a female interested in other females. Beware you may fall overboard and get stranded on a desert island though.
You can even gets splits of sparking wine, and maybe Champagne too, in cans. For example Niebaum-Coppola Sofia Blanc de Blanc sparkling wine. I haven't tried it but I hear it "doesn't suck real big time," meaning most people will probably like it.
Although straws, cans, and even the idea of these tiny bottles may turn off some connoisseurs, I'm in favor of anything that gets more people to drink the stuff and hopefully find they like it! Nothing against marketing gimmicks, although you won't find any Champagne splits in my cellar, or Miller High Life, the Champagne of Beers, in my fridge. Not that there's anything wrong with that . . .