24-year-old man uses his sister’s towel to clean the sink’s countertop in revenge for her boyfriend always leaving it wet: ‘I just get her towel and dry the sink (and floor if he lets it get wet too) with it’ – FAIL Blog

And yes, the sister shouldn’t be paying for this; if her boyfriend stays there three days a week, he has to have something of his own there- a sock, a t-shirt, something. If NOTHING I listed before, not the talking, nor the sign, nor anything works, he should definitely go for his t-shirts. If nothing works, he should ask his sister not to invite her boyfriend over when she is not around; problem solved!