How much water do you drink every day?

1. I drink two liters of water per day.
2. I drink 1.5 liters of water a day.
3. I drink ten liters of water every day.
4. I drink a ten-liter carton of water every day.
5. I drink a 5-liter pack of water every day.
(Are the answers all correct grammatically?)

Yes, all are correct.

And you are right that you can either use the word or the numeral when writing this kind of information.

ten-liter
5-liter
etc.

Let's analyze the grammaticality of each answer:

1. "I drink two liters of water per day." - This sentence is grammatically correct. It states that the person drinks two liters of water each day.

2. "I drink 1.5 liters of water a day." - This sentence is also grammatically correct. It indicates that the person consumes 1.5 liters of water daily.

3. "I drink ten liters of water every day." - This sentence is grammatically correct. It states that the person drinks ten liters of water on a daily basis.

4. "I drink a ten-liter carton of water every day." - This sentence is grammatically correct. It specifies that the person consumes a ten-liter carton of water daily.

5. "I drink a 5-liter pack of water every day." - This sentence is grammatically correct. It states that the person drinks a 5-liter pack of water daily.

All of the given answers are grammatically correct.