Mother's Ruin Punch

From Death & Co., a popular bar in New York. Cooking time = chilling time. Note: I don't know what they mean by "Black Market Tea" other than using black tea to infuse the vermouth. That is what I'm doing to make this punch. Their website doesn't clarify this.

• Ready In: 1 hr 20 mins
• Serves: 8

Ingredients

• 1⁄2 cup sugar
• 3⁄4 cup  chilled  club soda
• 1 1⁄2 cups  plymouth  gin
• 1 1⁄2 cups  fresh grapefruit juice
• 3⁄4 cup fresh lemon juice
• 3⁄4 cup  black market tea-infused sweet vermouth
• 2 1⁄4 cups  champagne or 2 1⁄4 cups  sparkling wine
•  grapefruit, thinly sliced wheels for garnish

Directions

1. Ahead of time: infuse black tea bags into the sweet vermouth at room temperature, 6 tea bags for a 750 mL bottle, or proportionately if you are preparing less. It will take less than one day to infuse -- gently swirl the bottle occasionally to see how dark it is getting. Usual infusion time is about 6-12 hours.
2. In a large pitcher, stir the sugar with the club soda until dissolved. Stir in the gin, grapefruit and lemon juices and sweet vermouth and refrigerate until chilled, about 1 hour.
3. Transfer the punch to a large bowl. Gently stir in the champagne and float the grapefruit wheels on top. Serve in punch glasses over ice.