Question

I need to install just ADB on customer´s PC to connect to android phone and install apk there. And because of SDK size is it possible to do it without installing whole SDK?

Answer 1

Yes you can

1. Firstly, you’ll need a program that can partially download contents of
   zip files from the internet.
2. Once that’s set up, go to the SDK
   download page and grab the link to the SDK.
3. In the zip file, navigate
   to "android-sdk-windows\tools"
4. From there, select only "adb.exe",
   "AdbWinApi.dll" and "AdbWinUsbApi.dll"
5. Download.

Source: http://twigstechtips.blogspot.in/2011/07/android-downloading-adb-without-sdk.html