Smoothie Help!

I had a smoothie called the Frozen Goat at Planet Smoothie and I'm trying to recreate it. It has about half a banana, some cocoa, some ice, yogurt, milk, vanilla extract, and coffee.

I put in about 1/4t vanilla, 50g vanilla greek yogurt, 1.5 oz. fat free milk, 50g banana, >1T unsweetened cocoa, and maybe 2 oz of coffee and about a cup of ice. It tastes decent but it's a little too bitter. Any suggestions on what I should change or add more or less of to add a bit of sweetness?

Thanks