A bath is 80l, a baked bean tin is 0.428l
Ergo you would need 900*10E9/(80/0.428) = 48,150,000,000 baths to use up those beans.
I do not know what the rate of bean-baths per hour is during CiN, so I'm going to make assumptions here. Assuming such a large number was done picture-in-a-picture style with each bath getting 10 seconds of air in the corner we could get 360 baths per hour requiring 133,750,000h of screentime, or a little over 15,000 years.
The real figure would be longer of course, as evidence suggests baked-bean baths are not filled as high as the same bath would be with water for bathing, also I think my volume statistic for the tin includes packaging.