Anything that taste like gin but isn't gin and is non alcoholic?!
Schweppes has an interesting Lemon/Lime & Bitters drink. They also make Indian Quinine Water and if you squeeze a lime and have it over ice you'll have a winner!
The flavor of gin comes mainly from juniper berries, and I can't think of anything else that uses them. Freesumpin's suggestion about Schweppes' is good, though it won't really taste like gin. Black licorice is another herbal flavor you might like, though it's more like ouzo or jaeger than gin.