Too much soy sauce can often mask the flavours of the sushi. (polite)
What are you doing?? There's no way you'll be able to even taste what your eating now that it's swimming in all that soy sauce. (rude)
The first example is the preferred way of telling someone that what they're doing is having a negative effect.
The second example would likely result in the person you are speaking to feeling ashamed and offended.
Only use the second one if you are certain that the person you are speaking to will take it as a friendly joke and won't be offended or if you do not want to be their friend anymore anyways. The first example is a far better choice.
You won't be able to taste anything with all that soy sauce.
The soy sauce will mask the taste of the sushi.
In order to explain adding too much of a condiment (a condiment is a sauce, for example soy sauce, tomato ketchup or salad cream) will disguise the taste, you can say:
You won't be able to taste anything with all that soy sauce.
This is an informal way of saying that with the amount of soy sauce the person is using, they will not be able to taste anything (in this case the ingredients in the sushi)
You can also say:
The soy sauce will mask the taste of the sushi/flavour.
To mask - To cover, to hide, to disguise, to cover with a mask.
I hope that helps!
調味料（醤油やトマトケチャップやサラダクリームのようなソースのこと）を入れすぎてしまうともともとの味を変化させてしまう、と説明するには
You won't be able to taste anything with all that soy sauce.
ということができます。
これは、その人が入れた醤油の量によってもとの味がしなくなってしまうことを伝えるカジュアルな言い方です。
（この場合は寿司の素材を想定してます）
または、
The soy sauce will mask the taste of the sushi/flavour.
mask - 覆う、隠す、変えてしまう、マスクを使ってカバーすること
参考になればうれしいです！
You're drowning the sushi with all that sauce! You'll only taste soy sauce!
'To drown the food with ___' We use this expression when a lot of sauce or liquid such as gravy or custard is added to a dish, whether it be a dessert or a savoury main course.
"You are drowning your Victoria pudding with custard - it will spill over the bowl!"
"You are drowning those french fries in tomato sauce: you'll only be able to taste ketchup!"
'To drown the food with ___' この文章は、グレービーやカスタードなど、メインかデザートかに限らず、たくさんソースがかかっている時に使います。
"You are drowning your Victoria pudding with custard - it will spill over the bowl!"
ビクトリアプリンをカスタードでおぼれさせる気かい。ボールからこぼれているよ。
"You are drowning those french fries in tomato sauce: you'll only be able to taste ketchup!"
フライドポテトをケチャップでおぼれさせるきかい。ケチャップの味しかしないだろう。
The dish is only meant to be eaten with a small amount of sauce.
To say that something will "overpower" the taste of the dish will let them know that the flavour of the sauce will be too intense or strong to taste the rest of the meal.
Or you can explain to them that the dish is supposed to be eaten with a small amount of soy sauce, in order to experience the dish the best way.
Go easy on the soy sauce, you won't be able to taste the fish!
You'll taste nothing but soy sauce if you overdo it.
Sushi has a subtle flavor so don't use too much soy sauce.
If something has a subtle flavor it means that it is not very strong.
Subtle is pronounced like ''suttle''.
A common phrase is also to ''drown'' you food in something or for it to be ''swimming'' in it.
Examples:
Don't drown the sushi in soy sauce, you won't be able to taste the sushi.
The sushi is swimming in soy sauce!
「subtle flavor」は、味があまり強くないことを表します。
「subtle」は「suttle」のように発音します。
ほかに「drown」や「swim」もよく使われます。
例:
Don't drown the sushi in soy sauce, you won't be able to taste the sushi.
（しょうゆをべったり付けちゃだめ、スシの味がしなくなるから）
The sushi is swimming in soy sauce!
（スシがしょうゆでヒタヒタになってるじゃん）
You wont be able to taste the sushi as well with all that soy sauce
All that soy sauce might mask the flavour of the sushi
With all that soy sauce you might not taste the flavour of the sushi
If you want to be polite then you would say 'all that soy sauce might mask the flavour of the sushi'
To mask something means to hide it so it wont be as obvious or as tasty
The other 2 are still polite but might come across as slightly ruder depending on who you are eating with (as everyone has their own opinon and likes things different)
相手の気持ちを考量して言う場合は、”All that soy sauce might mask the flavour of the sushi"（そんなにたくさんお醤油をかけると、お寿司の風味がわからなくなってしまうかもしれませんね）と言ってみるといいかもしれません。
”To mask xx"は「○○を隠す」という意味があり、「不味くなる」をオブラートに包んだ言い方になります。
他の二つの例文も丁寧な言い方ではありますが、相手によっては失礼だと思われてしまうかもしれません（人それぞれの意見や嗜好があるので）。
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