Collider Problems

I am trying to add a drinking mechanic to my game but I have yet to get it to work:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class Drinking : MonoBehaviour {
5.     public int thirst = 50;
6.  
7.     void OnTriggerStay(Collider other)
8.     {
9.         if (other.gameObject.tag == "Drink" && thirst < 100 && Input.GetKeyDown("e"))
10.                         thirst = thirst + 25;
11.     }
12.  
13. }

Anyone know what I might be doing wrong?

EDIT:
I got it to work. All I had to do was expand the trigger around the player.

 

If the game object does not have rigid body I think ontrigger method won't be called

 

A cup, which is the object i'm using, does have a rigidbody attached. But thanks anyways!