Maybe not the simplest option but also works
iex(1)> template = "http://somesite.com/?i=#<%=id%>&lang=#<%=language%>&type=api&api_v=1&api_type=#<%=data_type%>"
"http://somesite.com/?i=#<%=id%>&lang=#<%=language%>&type=api&api_v=1&api_type=#<%=data_type%>"
iex(2)> EEx.eval_string(template, [id: 1, language: "pt-BR", data_type: "json"])
"http://somesite.com/?i=#1&lang=#pt-BR&type=api&api_v=1&api_type=#json"
