電子レンジで食べ物を温める時は heat up を使います。
例文：
I heat up my lunch in the microwave at the office (オフィスの電子レンジでお弁当を温めます）。
なので、一番自然な言い回しはこの heat up を使った表現です。もう少し熱くしてくださいと言いたければ、can you heat it up more please? となります。
Can you make it hotter please? でも通用しますし、全然大丈夫ですが、なるべく heat it up という言い方の方が自然です。
どうぞご参考に。
温めてもらうことは「Heat」してもらう事です。
したがって、「Could you heat it up a little more please?」を提案しました。
ここでのポイントは、何かをお願いする時は必ず「Please」を入れる事です。
「Please」を入れずに「Could you heat it up a little more?」と言うと、すごく横柄に聞こえます。
また、文書の頭の方に「Please」を持ってきても大丈夫です。
「Please could you heat it up a little more?」などと。
怒ってすごく失礼に言いたいなら次の英語が良いと思います。
- Stick this back in the microwave, it's not warm enough（もう一度レンジに入れろ。十分に温まっていない）
Please leave it in the microwave for another minute or so.
Could you please heat it up a little more?
1. Please heat it up in the microwave for another minute or
so more.
To heat up means to warm up.By requesting this for another
minute or so more, the store assistant will understand that
you want it heated until it's at the right temperature for you
to enjoy.
2. Could you please heat it up a little more?
A little more means for a bit longer or for a little while more
until it is just perfect to eat right away.
1. Please heat it up in the microwave for another minute or so more.
（もう1分かそれくらいレンジで温めてください。）
To heat upは、温めるという意味です。いい温度になるまで温めてほしいことをお店の人はわかってくれるでしょう。
2. Could you please heat it up a little more?
（もう少し温めてもらえますか？）
A little moreは、もう少し長くという意味です。
Please would you put it back in the microwave for another minute. It still feels cold.
Please will you heat it for a further minute.
Always begin a request with "please". It is the polite thing to do.
Please would you put it back in the microwave for another minute. By using "it still feels cold" you are giving the person a reason for your request.
何かをお願いするときは常に"please"をつけましょう。丁寧な表現になります。
Please would you put it back in the microwave for another minute.
（もう1分電子レンジに入れてもらえますか？）
"it still feels cold" （まだ冷たい）と言うことで、そのお願いに対する理由を伝えることができます。
I'm sorry, it's not warm enough for me, can you warm it up some more please?
I'm sorry, it's still cold, can you warm it up some more please?
In this case, to be polite and not risk offending the person working in the store, it's best to start with, "I'm sorry" followed by one of the above options. Being not warm enough and still cold, mean the same.
この場合、店員さんに丁寧に、気分を害さないように、"I'm sorry"（すみません）と始めるのがベストです。 Being not warm enough（まだ温かくない） とstill cold（まだ冷たい）は同じ意味です。
Could you please warm it up a bit longer? It's still a little cold.
Please warm it up longer.
When you want to ask a store assistant to warm up your food a bit longer in the microwave; then you may ask in the following ways:
-Could you please warm it up a bit longer? It's still a little cold.
-Please warm it up longer.
以下は、お店の人にレンジで食べ物をもう少し温めて欲しいことを伝えたいときのフレーズです。
-Could you please warm it up a bit longer? It's still a little cold.
（もう少し長く温めてもらえますか？まだ少し冷たいです。）
-Please warm it up longer.
（もう少し温めてください。）
"If possible, could you please warm it up for a little bit longer?"
If you were at a convenience store and bought a bento and had the clerk warm it up for you in a microwave, but it was too cold and you would like it to be warmed up more, you could say either of these two questions:"Could you microwave it a little longer please?" or "If possible, could you please warm it up for a little bit longer?".
コンビニで、お弁当を買って店員さんに温めてもらったけれど、まだ冷たくてもっと温めて欲しいときのフレーズです。
"Could you microwave it a little longer please?"
（もう少し長めに温めてもらえますか？）
"If possible, could you please warm it up for a little bit longer?"
（大丈夫なら、もう少し長く温めてもらえますか？）
This is still not hot yet, can you pleae put it back in the microwave?
If you have a situation where you bought something and it's coldyouo can ask ten to heat it up for you. Sometimes the food that you bought may still not be hot enough to your liking, in such a case you can ask them the following:-
1. Could you heat that up a little more please?
2. This is still not hot yet, can you please put it back in the microwave?
食べ物を買ってそれが冷たいときには、温めてほしいとお願いできますが、温めてもらったものがまだ十分に温まっていないときには、次のように言えます。
1. Could you heat that up a little more please?（もう少し温めてもらえますか）
2. This is still not hot yet, can you please put it back in the microwave?（まだ温まっていないので、もう少し温めてもらえますか）
These two are the best way of expressing yourself. The first sentence seems to be more polite because of the word "could" in it, although, "may" gives the sentence a more positive meaning too
Do you think you could heat it for like another minute or two? It's still kinda cold.
Would you mind microwaving it a little longer, please?
Ootchanさん
ご質問どうもありがとうございます。
様々な表現があると思いますが、いくつか自然な表現を紹介します。
・Do you think you could heat it for like another minute or two? It's still kinda cold.
・Would you mind microwaving it a little longer, please?
--- kinda = kind of（なんかまたはちょっと）の略で、少しカジュアルな言葉です。
--- would you mind + 動詞+ing = ～してくれませんか？
お好みに合わせて使い分けてみてください。
ご参考にしていただければ幸いです。
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