Infusing gin with cucumber brings out the spirit's floral flavor, which is the perfect match for sweet-tart grapefruit soda in this elegant brunch cocktail.
Place cucumbers in a small pitcher. Mash with a muddling tool or a wooden spoon until cucumbers release juices and break down into small pieces. Add gin, cover, and refrigerate at least 12 hours and up to 3 days.
Place ice in each serving glass. Pour 1 1/2 ounces cucumber-infused gin into each and top with soda. Stir once, garnish with cucumber slices, and serve immediately.
A single large ice cube -- made with a special ice-cube tray -- works best for fizzy cocktails. Smaller cubes melt faster and make the drink go flat quicker.