4-month sleep regression hit us like a truck — survival mode tips?

Baby slept 5-hour stretches at 3 months. Now at 4 months she's up every 45 minutes and I cannot function. The 4-month regression is real and it is brutal. We're in a HDB so CIO is not realistic for our neighbours. Anyone come out the other side? What approach worked without full CIO? How long did the regression last for you? I'm running on 3 hours of broken sleep and crying into my coffee.