He must drink as little as three litres of water per day.

English as a Second Language English Vocabulary, Grammar and Idioms
1

He must drink as little as three litres of water per day.

Could you help me parse the bold phrase?
Here is what I got so far.
The first “as”: adverb
“little” = adverb

2

The phrase is illogical. Three litres of water is a lot of water:

He must drink as much as three litres of water per day.

3

Thanks. I will change my sentence to “He must drink as much as three litres of water per day.”
I would like to know how to parse as the part “as much as three litres of water per day”.