According to the Orbea website, the RS range extender battery cage is compatible with a "standard" size water bottle on the Rise M,H, URRUN & KEMEN series bikes.
RS Range Extender GEN 0
RS Range Extender GEN 1
It isn't clear about the X35 kit for the Orbea GAIN.
X35 Range Extender Kit
You can try downloading the user manual to see it any dimensions are listed.