If you don't have or don't want to use Sauvignon Blanc, you can use Pinot Grigio, Riesling, or another white wine. I'm not a fan of Chardonnay (because of the prominent oak flavor) so I wouldn't use that. Try flavored sparkling waters for some more flavor. You can also use ginger ale or lemon-lime soda in place of the club soda for a different flavor. To add extra flavor you can muddle (or just drop in) fresh fruit and herbs. You can skip the bitters if you don't have them or don't enjoy the flavor.