This is the 13142nd most frequent Russian word.
меньше
Less; smaller.
Here, "меньше" is used as an adverb modifying the verb "пить", indicating a quantity decrease.
Я стал меньше пить кофе.
I have started drinking less coffee.
In this sentence, "меньше" is used as a comparative adjective to compare the number of apples between two boxes.
В этой коробке меньше яблок, чем в той.
There are fewer apples in this box than in that one.
Here, "меньше" is a comparative form of the adjective "малый", advocating a reduction in speaking actions for emphasizing action-taking.