SBT respects the usual environment variables for http/https proxy settings:

Set the below environment variables before invoking SBT and it should work.

SET JVM_OPTS=-Dhttp.proxyHost= -Dhttp.proxyPort= -Dhttps.proxyHost= -Dhttps.proxyPort=

SET JAVA_OPTS=-Dhttp.proxyHost= -Dhttp.proxyPort= -Dhttps.proxyHost= -Dhttps.proxyPort=

If you have username / password for your proxy authentication, then add below properties:

-Dhttp.proxyUser=
-Dhttp.proxyPassword=
-Dhttps.proxyUser=
-Dhttps.proxyPassword=