The sweetness/healthiness of your milkshake depends on the ingredients. If you're using ice cream, then yes, it will be really sweet and not at all healthy. Why not try a protein shake, rather than a milkshake? Try a scoop of vanilla protein powder with 1/2 cup milk and 1/2 cup water, 1 cup frozen fruit chunks... blend and enjoy. Protein will keep you feeling fuller longer and it won't spike your blood sugar
like a regular milkshake will do.