An example is included in the help docs:

https://developer.salesforce.com/docs/atlas.en-us.mc-apis.meta/mc-apis/retrieving_data_from_a_data_extension.htm

The API SDK are wrappers for SOAP and REST and are not required to be used

An example is included in the help docs:

https://developer.salesforce.com/docs/atlas.en-us.mc-apis.meta/mc-apis/retrieving_data_from_a_data_extension.htm

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 <soapenv:Header>
 <wsse:Security soapenv:mustUnderstand="1" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
 <fueloauth xmlns:ns1="http://exacttarget.com">XXXXXXXXX</fueloauth>
 </wsse:Security>
 </soapenv:Header>
 <soapenv:Body>
 <RetrieveRequestMsg xmlns="http://exacttarget.com/wsdl/partnerAPI">
 <RetrieveRequest>
 <ObjectType>DataExtensionObject[Example DE]</ObjectType>
 <Properties>EMAIL_ADDRESS</Properties>
 <Properties>CUSTOMER_ID</Properties>
 <Properties>FIRST_NAME</Properties>
 <Properties>SITE_GROUP</Properties>
 <Filter xsi:type="SimpleFilterPart">
 <Property>EMAIL_ADDRESS</Property>
 <SimpleOperator>equals</SimpleOperator>
 <Value>[email protected]</Value>
 </Filter>
 </RetrieveRequest>
 </RetrieveRequestMsg>
 </soapenv:Body>
</soapenv:Envelope>

The API SDK are wrappers for SOAP and REST and are not required to be used