Plant-based drinks have increasingly become a regular product in the market. The range of raw materials available creates an abundance of products with various properties. For product optimization purposes, it is imperative to fully characterize the product, especially in terms of its physical stability. This review aims to summarize the techniques currently available to characterize and understand the underlying factors describing the physical stability of plant-based drinks. The methods discussed range from general methods that have been widely used to specific fingerprinting spectroscopic techniques such as UV-VIS, FTIR, NIR, Raman, Fluorescence Spectroscopy, and NMR. The benefit and trade-off of each method is discussed in relation to its application for plant-based drink products. In addition, the classic colloid theory (the electric double layer) is mentioned to explain the separation phenomena which follow the discussion on available mechanisms to improve the system (electrostatic and steric stabilization mechanism).