After many years my Polar brand water bottle cap nipple thing broke off. The water bottle still works sort of but dribbles and is generally terrible now.

Supplies

So I fixed it using vinyl electrical tape, a stainless steel drinking straw, & a piece of shrink tubing.

Step 1: Cap Prep

Remove any remaining rubber pieces stuck in the cap. I used needle noses to pull them out. Drill through the spout stopper thing. I found it easier to drill from the inside out. Clean up the hole with a chamfer bit or a sharp Xacto knife.

Step 2: Mouthpiece

I was able to use the top of the mouthpiece to finish off the cap. I needed to do a two layer wrap of vinyl electrical tape to make a better seal to the cap.

OK. So now we have a working water bottle again. There is no longer a seal that closes the water bottle. So what? For me, I fill it with water and none slobbers out going over rough terrain. All good. Back to normal!

Step 3: One More Thing

I put a 30mm piece of electrical shrink tubing (Home Depot) over the end of the stainless steel straw leaving it about 4mm from the end. I then shrunk it to the straw with a heat gun. You can also use a cigarette lighter if you're careful. I then jammed it into the cap. Perfect fit!

Step 4: Operation

Fill the bottle with water and screw down the cap. Squeeze. Water shoots out like a drinking fountain. No more Taco Neck required to get hydrated. It worked out that the bottle could be emptied all except for the last 50ml. Not bad.