毎日外食しているって英語でなんて言うの？

We can say "I eat out" to mean that we eat food that is prepared outside our home.

You can also say "Lately, I don't eat home-cooked meals." if you don't eat home-cooked meals it may mean that you eat food prepared outside of your home.

If you mean, 'Eating in the open air' as opposed to 'eating inside'. then use 'outside'.
If you mean eating in a restaurant or cafe as opposed to eating at home, then use, 'out'.

I eat takeout every day.

This is a casual and native expression used to express that you do not eat at home every day.

Example:
Person: Do you like to cook?
You: I eat takeout every day.

I get takeaway every day.

This the British English way to say the previous expression. It is also casual.

Example:
Person: Do you like to cook?
You: I get takeaway every day.

I like to eat out almost every day.

This is another casual native expression used to express that you do not eat at home every day.

Example:
Person: So, do you cook a lot?
You: I like to eat out almost every day.

Note: The expression "eat out" means to get food from a restaurant.

Of late means recently or in the last couple of days.
For example:
"She'd been drinking too much of late"

I honestly prefer to eat outside every day. Don't like to cook at home - this is the perfect way to explain what do you want to say. The first sentence is good too but has a lack of details.

There are different types of ways you can say you eat outside, and depending on how you use them in a sentence it can have a different meaning.

I eat out everyday. - You are informing the person that you do not eat at home, eating out can mean that you eat outside, it could be at a restaurant or a fast food place.

I'm always eating outside of my house. - You do not eat at home, but it does not necessarily mean that you are eating at a restaurant or a fast food. It could just mean that you eat out in the open air, at a friends or work.

I don't have time to cook, so it's easier to eat out. - You do not have time to cook at home, maybe you work a lot so it's easier to buy food.

You can use these phrases differently, and switch them up. For example:

Whenever I don't feel like eating at home, I go out to eat. - sometimes you are tired of cooking or your own food, it's easier to eat out and taste other food. This is a way to express that you would like to eat out, because you are no longer interested in the food at home.

I eat at restaurants everyday. ---> This is probably the most common way to describe that you don't cook at home and instead go outside of your home to eat.

I eat out everyday. ---> the preposition, "out," can be used to replace the words, "at restaurants," to express the same idea that you leave home to eat.