Pretty sure it's just going super low purity (increases fluid production) and spamming the everliving shit out of the bakery.
As far as I can tell it is by far the most profit per hour, and it's essentially limitless.
Some of the activities that come close but are extremely limited in availability:
-Thieving on danube street when you hit the wine cellar or safe (extremely variable $/hr)
-Stealing gold bars from the docks (complete RNG and very bad chances, super super unreliable, but as much as 2k/hr if you open only one container at the gates and it has a bar)
-Danube street mansion party via charlie (once per week, base of ~670/hr if you accept the money, can steal during breaks for even more)
-Milking cows at the farm, but limited to effectively 1.5hr of work per day (at 288/hr with max tending and farm level)
-Modelling work with max exhibitionism (500/hr or more, once per week)
-Spa massages are available all the time, but the average rate is only 100/hr with maxed skills. The chance to get a horny customer is only 1/5, and even those only come out to about 500-550/hr
Growing from the farm is pretty decent money too, but throughput is limited by your business fame and the yields are incredibly variable (as much as 10x difference depending on RNG). It's too difficult to calculate a number for this. Takes very few clicks to cycle though... so could be a good option on the side?
Oh and at the complete opposite end of the spectrum, diving at the lake takes only one minute per dive... but the random events will eventually max out your stress (and then trauma), so there is a practical limit.
Still, the $/hr for that is almost unlimited? You could savescum diving and resurfacing to change the events and avoid all the stress? Millionaire on day one!
