サービスでアイスがつきます。って英語でなんて言うの？

Depending on the exact situation, you could explain that there is complimentary ice cream in three flavours, or you could just ask which flavour of the complimentary ice cream they would like to choose. Although they may then say: "I don't want the complimentary ice c ream, I'd like something from the menu instead."

It is not always necessary to offer so much information. The restaurant gives ice cream away for free so you can begin your question with which flavour they would like, because they would mostly likely always agree to something free. Another word for complimentary is 'on the house'. "This ice cream is on the house". It means the company is paying for it.

"As a bonus, we give ice cream of the following flavours vanilla, chocolate and matcha." "We also give a scoop of ice cream of your choice vanilla, chocolate or matcha on the house." Both of these expressions are exactly what you want to say to your customer. The most common and popular that I personally have been told by restaurants here in the U.S. is the second one. When they say "On the house" it usually means that is complimentary. You rarely hear a restaurant say complimentary. For example, if you buy one beer the next one is on the house or free! The first expression is mainly used at places where kids go to a lot such as a restaurant that caters to kids because the word bonus is more popular amongst youngsters and they can relate that word with a gift or something free, complimentary.

We offer free ice cream. Would you like some? We have vanilla, chocolate, and matcha. Which would you like? Would you like some free ice cream? We have vanilla, chocolate, and matcha. I would be happy to bring you some ice cream. It's free. What flavor would you like? Are you ready for some free ice cream? I will be happy to bring you some. Are you ready for your ice cream? It's complementary and we have vanilla, chocolate, and matcha flavors.

"Our guests receive complimentary ice cream, our flavors are vanilla, chocolate and matcha, what would you like?" To 'Receive' something usually suggests that something is given to you, ex. "I received 10 birthday cards for my birthday". when using 'complimentary' this is used when something is given to someone else, usually by a business, for free. ex. "Here is your complimentary bottle of wine with your meal". another term for 'complimentary' is "On the house", ex. "This bottle of wine is on the house".

Complementary is not used a lot in normal day to day conversation anymore. You can use words such as: free, bonus, included, no cost, on the house, or part of the meal. If it is an upscale or expensive restaurant complementary will probably still be used. You can say would you like some ice cream it is free. Would you like some ice cream it is included in the price of your meal. Would you like some ice cream it is part of the meal.

You could tell the customer that you offer complimentary ice cream, followed by telling them which flavors you offer. If you would like to be more polite, you could first ask the customer if they would like ice cream, followed by telling them which flavors you offer.