Assets/Scripts/HydrationBar.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class HydrationBar : MonoBehaviour
{
 
    private Slider slider;
    public Text hydrationCounter;
    public GameObject playerState;

    private float currentHydration, maxHydration;
    // Start is called before the first frame update
    void Awake()
    {
        slider = GetComponent<Slider>();
        
    }

    // Update is called once per frame
    void Update()
    {
        
        currentHydration = playerState.GetComponent<PlayerState>().currentHydration;
        maxHydration = playerState.GetComponent<PlayerState>().maxHydration;

        float fillValue = currentHydration/maxHydration;
        slider.value = fillValue;
        hydrationCounter.text = currentHydration+"%";

    }
}