Apollo mutate without Hook in React custom Hook

I'm calling a custom hook within a React Component:

const [CallMe, { loading, data, error }] = useCustomHook({
    onCompleted(res) {
        console.log(res)
    },
    onError(err) {
        console.log(err)
    },
})

Which is initiated via an onClick event:

onClick={() => CallMe() }

The custom hook consists of the following:

export function useCustomHook({ onCompleted, onError }) {

/**
 * Use State
 */

const [loading, setLoading] = useState(false)
const [data, setData] = useState(null)
const [error, setError] = useState(null)

/**
 * Get Thing
 */

function GetThing() {
    setLoading(true)
    callExternalApi
        .method()
        .then(({ data, error }) => {
            setLoading(false)
            if (error) {
                setError(error)
                onError(error)
            }
            if (data) {
                CALL TO MUTATION NEEDED HERE (NON HOOK)             
            }
        })
}

return [GetThing, { loading: loading, data: data, error: error }]
}

When data has successfully been returned I want to fire a Mutation, however I don't want this to be done via the useMutation Apollo hook.

Therefore my question is how would I fire this mutation in a none hook manner that will still allow me to update the Apollo Cache on response all within this custom hook?

I understand that I can simply do a HTTP request via Fetch, but this wont give me the inMemoryCache advantage that Im using with throughout the app. Would I have to intializeApollo within the custom hook?

Any thoughts or suggestions are welcome.

It would appear that within my custom hook I can import Apollo Client, this then gives me the ability to use mutations and queries.

import { useApolloClient } from '@apollo/client'

Then within your exported custom hook:

client
        .mutate({
            mutation:MUTATION,
            variables: {
                Input: input,
            },
        })
        .catch((error) => {
            console.log(error)
        })
        .then((result) => {
            console.log(result)})