Poor Mama

Listen up, buttercup. This "yo mama" joke is saying that yo mama is so broke, she can't even afford to buy hand sanitizer from the store. Instead, she has to whip up her own batch, probably using some questionable ingredients she found in the back of the fridge. I know you don't understand what "broke" means, but it's like when you try to buy candy and realize you only have lint in your pocket.