define a state: const [repeater,setRepeater]=useState(0) in your useEffect pass it as second argument so whenever it is changed, your useEffect would run again. Now let's take care of the 10 second intervals with this piece of code: setTimeout(() => setRepeater(prevState=>prevState+1), 100000); and finally implement it like tis:

   useEffect(() => {
  const fetchData = async () => {
    setIsLoading(true)
    const response = await coinGecko.get("/coins/markets", {
      params: {
        vs_currency: "usd",
        ids: watchList.join(","),
      }
    })
    setCoins(response.data)
    setIsLoading(false)
  }

  fetchData()
  setTimeout(() => setRepeater(prevState=>prevState+1), 100000);
},[repeater])