Fill a 16 oz cup with ice cubes, packing them about three-quarters of the way up the cup.
Pull 2 shots of fresh espresso into a separate small cup or glass. If using cold brew concentrate, measure out 2 oz and set aside.
Pour the 4 oz of energy drink concentrate over the ice in your main cup. This provides the signature energy boost and flavor profile.
Add the 2 oz of milk or half-and-half to the cup, stirring gently to combine with the energy drink.
Pour the hot espresso shots into the cup carefully. The hot espresso will slightly melt the ice and blend with the cold ingredients, creating the signature Rebel flavor.
Add 0.5 oz of simple syrup or vanilla syrup if desired for extra sweetness, then stir well to combine all ingredients.
Top with whipped cream if desired and serve immediately with a straw. Enjoy your copycat Dutch Bros Rebel!