A robot bartender is mainly a fluid-handling project. The best DIY architecture uses peristaltic pumps, because the liquid only touches the tube, not the pump internals. That makes cleaning easier and keeps sticky liquids away from motors.
Avoid open gravity-fed reservoirs unless you enjoy leaks. Use capped bottles, food-safe silicone tubing, one pump per ingredient and a rinse line. A load cell under the glass catches missing-glass errors and can measure dispensed liquid by weight for calibration.
The first version should mix 4-6 ingredients, not twenty. Add a web UI with recipes, pump calibration values and a rinse button. RoboHub can generate the enclosure and firmware, but you still need to use food-safe parts and clean tubing after use.