What's a good use for cheap sparkling wine (other than vinegar)?

Make a simple syrup with it and use to make a fresh grapefruit compote..so delicious.

I would use it to poach pears.

Reduce and use as a glaze for chicken. Make jelly out of it. Punch. Granita. Sub for water in Agua Fresca with pineapple.

Add a tablespoon or two of elderflower syrup (other syrups work well, too--I am using a spiced pear syrup for the holidays) or make an Aperol or Campari spritz.

Another thought, raclette. Drizzle some on sliced baguettes, top with raclette slices, finish under a raclette maker or in the oven. Serve with cornichons.

If it's good enough, just not great, kir royales (originally made with cassis, but now with any variety of additions). Otherwise, I second pierino's sorbet suggestion. Sorbets made with sparkling wine are remarkably delicious.

Mimosa's. With either orange or peach juice and the sparkling wine.

I think you could also some of it for quick breads that call for soda water.

Sorbet, assuming you have an ice cream maker, although I'm not sure it's "a good use." You can also try it out in mushroom soup.