You can potentially get sudo on Android, but the ability to do so largely depends on the device. I guess there may be some devices which run on Linux and lock the user out from installing their own version or accessing super-user, but that’s a lot less common.
I would say that Android is not Linux, but it is based on Linux. The ACK is a based on the core Linux kernel, but with additions that aren’t found in mainline and a fairly different userspace and lack of a GNU C library. They’re more like cousins than siblings at this point.