- Prepare cake batter and bake in 13x9-inch pan as directed on package. Cool cake in pan 15 min. Pierce cake with large fork or skewer at 1/2-inch intervals.
- Add boiling water to gelatin mix in small bowl; stir 2 min. until completely dissolved. Stir in cold water; slowly pour over cake.
- Refrigerate 3 hours. Meanwhile, toss berries with drink mix.
- Refrigerate until ready to serve.
- FROST cake with COOL WHIP; top with berries.