Depends if you want to go into ketosis or not. There are ketogenic full meal replacement plans out there. I lived on nothing else for 3 months a couple of years

Depends if you want to go into ketosis or not. There are ketogenic full meal replacement plans out there. I lived on nothing else for 3 months a couple of years ago, in the UK. 28 drinks per week for 4 weeks, then 21 + 7 protein bars. You could presumably avoid ketosis and weight loss by adding in caloric drinks, though obviously not intended. Afraid I don't know of any in the US, though (assuming location based on time). Medifast seems the closest but they advocate meals alongside the replacement.