H2O involves H-bonding ,whereas BeF2 is a discrete molecule
electronegativity of F is greater than that of O
H2O is angular and BeF2 is linear
H2O is linear and BeF2 is angular.
Because of linear shape, dipole moments cancel each other in BeF2 (F→Be←F) and thus, it is non-polar , whereas H2O is V-shaped and hence, it is polar.