A very similar method extraction approach can be applied to Consumer actions, as in the following:

.doOnError(error -> {
    Toast.makeText(this, "We couldn't reach internet - falling back to 
    local data",
            Toast.LENGTH_SHORT)
            .show();
})

Here, the error handling code can be extracted with a method:

showToastErrorNotification()

So, the line becomes this:

.doOnError(showToastErrorNotification())

Also, the method itself contains this:

@NonNull
private Consumer<Throwable> showToastErrorNotification() {
return error -> {
        Toast.makeText(this, "We couldn't reach internet - falling 
        back to local data",
                Toast.LENGTH_SHORT)
                .show();
    };
}

This way, the actions (consumers) become more descriptive and take less space in the flow itself.