Meaning
To drink water by measure (Ezek 4:11), and to buy water to drink (Lam 5:4), denote great scarcity. To drink blood means to be satiated with slaughter.
The Jews carefully strained their drinks through a sieve, through fear of violating the law of Lev 11:20, 23, 41, 42. (See Matt 23:24. "Strain at" should be "strain out.")