Definitely need to bleach old shaker bottles. I would do that if you waited more than a day to wash it.
My worst mistake on this front was leaving the country and not having washed one of my old shaker bottles I used the day OF my flight. When I returned to the U.S. 2 weeks later and went to the gym, I used a fresh, new shaker cup to make my PreWO, put it in my gym bag, and left. I usually re-use my pre-wo bottles as water bottles at the gym. So I took out a shaker cup, filled it up, continued drinking it throughout my workout. It was a hard workout, so drinking was more of a thing to mitigate pain/stay alive. After refilling it, I noticed the water was a funky color. When I took a drink, it was awful. Then it dawned on me - this is a 2 week old shaker cup. Disaster!