I've used Crystal Light fruit punch and low sugar cranberry juice as a base in place of regular fruit juices before. I don't know how much protein/fat you're wanting to get in your smoothies, but my favorite is:
-1 cup unsweetened almond milk
-1 scoop whey protein (fat free greek yogurt or other protein powders will work too)
-2 Tbsp ground flax seed (for healthy fat and fiber)
-1 cup frozen strawberries, unsweetened
-1/2 cup frozen blueberries, unsweetened
-1 cup spinach (I add leafy greens to everything I can, and it doesn't change the taste)
-ice
Nutrition breakdown:
304 calories, 9 g unsaturated fat, 39 g carbs, 12 g fiber, 24 g protein, 288 mg sodium, 25% fat, 45% carbs, 30% protein
It's a meal within itself, and it's really filling with the added fat, protein, and fiber. It fits well into the ratios I set for myself, and it's not as pricey as having Jamba Juice all the time!