Combine everything in a blender (use the lower measurements of stevia and pineapple extract) and blend until smooth. Taste and adjust sweetener and pineapple extract to taste, blending again after adjusting.
Notes
Alternatively, if you find pineapple flavor/extract that you like, use 1/4-1/2 teaspoon of that and omit the frozen pineapple. Nutrition is then: Calories: 152 cal, Carbs: 3g, Fiber: 1g, Fat: 15g, Protein: 1g