The objective of this study was to evaluate sorption properties, to characterise selected physicochemical properties, and to conduct instrumental colour analysis during storage of four instant plant beverages purchased on the Czech market. The evaluation was conducted for four powdered instant plant beverages: oat (I), buckwheat (II), rice (III), and corn (IV) ones. The sorption properties of the investigated products were analysed with the static method by determining isotherms of water vapour sorption. The scope of the study included water activity in the range from 0.07 to 0.98 (25°C). The moisture equilibrium of the system settled within 45 days. Based on the initial weight of the product and changes in water content, equilibrium contents of water were computed and water vapour sorption isotherms were plotted. BET equation in water activity range of 0.07≤a_w≤0.33 was used for mathematical interpretation of the course of water vapour sorption isotherms. Applicability of the BET model for the description of plotted isotherms was evaluated based on values of determination coefficient (R²) and standard error of estimation (FitStdErr) that were determined with the use of Jandel-Table Curve 2D v 5.01 software. The evaluation of physicochemical properties of the analysed instant powdered products was carried out based on the assessment of granulometric composition, loose and tapped bulk density, Hausner ratio (HR), and Carr index (I_Carr). Colour parameters L^*, a^*, andb^* were determined in the international CIE system using a Konica-Minolta CR 400 colorimeter for standard observer 2º and illuminant D 65. The conducted analyses demonstrated that differences in the sorption as well as physicochemical properties of the investigated instant plant beverages were determined, most of all, by the heterogeneous raw material composition of the analysed products.