Is it permissible to give a poor brother a portion of money from forbidden investment certificates to buy clothes or cover travel expenses, or to use part of it to pay a phone bill?

All types of investment certificates are forbidden (haram). The usurious interest earned from them must be disposed of by spending it on the poor, the needy, and for the general welfare of Muslims. As for the principal, it is permissible (halal) for its owner. It is permissible to give to a poor brother from this interest, but it is not permissible to use it to pay personal bills.