Three ways to open drinking coconuts

This can be done using household items.

With the heel of a chef's knife. See video.

Hand drill tool

Can work like a charm if you hit the right spot, or be exasperating and require another tool (for stubborn coconuts).

See here $7:

I recommend a larger mallet be used with it (it is much easier that way).

See here $15:

With a stainless steel tapping machine (lever operated).

Have not personally used, but looks grandma friendly.