How can I connect to my other phone's internet?

VPN
1

Is there some sort of a VPN app that I can use on my phone which would allow me to connect to the IP address my other phone connects to?

Say the ip address of my other phone’s internet connection is 11.111.11.111. I want my phone to connect to that IP address via my other phone?

Is this possible? How? I’m guessing some sort of a tunnel between the two phones?

2

No. That’s not how VPNs work.

3

I don’t think there’s any VPN servers available for Android or iOS. You could use a router or PC connected to your other phone to act as the server.

What are you actually trying to achieve though. This looks a lot like an XY problem.

4

I have services on X phone that require the same IP as Y’s