The phrase "do for" can have a variety of synonyms depending on the context of the sentence. It can be replaced with "help," "assist," "aid," "serve," "support," "take care of," or "provide for." To express the idea of something being sufficient or satisfactory, it can be replaced with "suit," "suffice," or "be adequate." In the sense of causing harm or damage, "do for" can be replaced with "ruin," "spoil," "destroy," "hurt," or "injure." Depending on the context and intention of the sentence, choosing an appropriate synonym for "do for" is important in conveying the intended meaning effectively.