SPRAY 24 mini muffin pan cups with cooking spray. Slowly add tonic water and water to gelatin mixes in large bowl (gelatin will foam); stir 3 min. until completely dissolved. Skim off any foam.
SPOON 1 tsp. gelatin into each of 24 mini muffin pan cups. Place grape wedge into center of each cup. Refrigerate 5 min. Spoon remaining gelatin over grapes. Refrigerate 3 hours or until firm.
UNMOLD just before serving.