Answer
The other product is likely $HCl(g)$.
Work Step by Step
Create a balanced equation to find the other product.
The inputs are $XCl$ and $H_2O$.
Since the $XO_2$ output requires 2 oxygen atoms, 2 $H_2O$ molecules are required to balance the equation.
This leaves 4 molecules each of $H$ and $Cl$, so 4 molecules of $HCl$ are generated.
$XCl_4(l)+2H_2O(l)\rightarrow XO_2(s)+4HCl(g)$
