It is an alteration of the phrase "p*t*ng ina mo", meaning "m*therf*cker" or "your mother is a prostitute." Obviously it is some sort of curse. It is used to make fun of people who do not know Filipino language.

the thing that you don’t have when you’re phones percentage is over 20

"Put tank in a mall" is a play phrase for "putang ina mo" which is a Pilipino vulgarity that means fuck your mother.

Often used on Dota 2

Put tank in a mall is a word play. It is originally a Filipino foul word (phrase) "putang ina mo" which literally means "your mom's a whore". Put tank in a mall is often used in DOTA2 when Filipinos are asked to speak in English.