I like to clarify usage:

SETUPTOOLS_SCM_PRETEND_VERSION_FOR_MY_PACKAGE=$VERSION

That means if I have in pyproject.toml:

[project]
name = "qc-iodata"

the right forms is:

SETUPTOOLS_SCM_PRETEND_VERSION_FOR_QC_IODATA

So I can do in bash:
export SETUPTOOLS_SCM_PRETEND_VERSION_FOR_QC_IODATA=1.0.0a8