Loop the variants and check their names:
productFlavors {
vanilla {}
chocolate {}
}
applicationVariants.all { variant ->
println("Iterating variant: " + variant.getName())
if (variant.getName() == "chocolateDebug") {
variant.buildConfigField "boolean", "VARIABLE", "true"
} else {
variant.buildConfigField "boolean", "VARIABLE", "false"
}
}