他に何かご注文はございますか？って英語でなんて言うの？

In the UK, the most common form is probably: "Is that everything?' or, 'Anything else?' and either of those are acceptable. However, to be a little more formal and polite, you could use 'would' in the question form, which has the effect of making your query indirect rather than direct. "Would that be everything?"

This is a polite closing expression making sure the customer is satisfied and has everything they need. It can mean would they like to order anything else or simply just getting them something they might need like cutlery, water, etc. It seems a bit casual but it is used a lot in waitressing.

"Would that be all for you?": You would ask the customer at the end of their order to see if they would like to order anything else. "Would you like to add anything else to your order?": You could ask the customer if they would like to add anything to what they have already ordered. I hope this helps :)

The most important thing about being polite is your tone and making sure you smile. You can say something like: -Thank you for your order. Can I get you anything else? You can also say the list of things the person has ordered and then ask: will that be all?. Then after that you can say thank you.

When working at a restaurant, most waiters ask the customers if they want anything else, so it is not considered impolite. Of course, even a polite question can be considered rude depending on the tone. So be careful of that. But the most common way to ask if they would like to order something else is by making a suggestion. For example many people say something like: may I suggest or can I interest you in a___? These are very common and will be always considered polite. For example: May I suggest our strawberry cheesecake? Can I interest you in a delicious appetizer?

Depending on the restaurant that you work at, if it is a formal Japanese restaurant I would use the phrase "Is there anything else I can get you?", however in a fast food or lower price point restaurant I would simply use the phrase "Something else"? Both are polite. You could also be specific in your question such as "Would you like to order dessert?" or "Can I get you anything to drink?"

The two sentences you see provided above are terrific ways to ask your customer if they want anything else with their order. In the first sentence you will notice the verb add. This verb means to join one thing to another thing. This is a word that is common in our everyday conversation and it would make a great addition to your vocabulary.