Summary

The STANLEY 10-01435-001 Utilty XL Travel Cup 32 oz - Green
is inexpensive (about $10) and fits automobile beverage holders well. However, it doesn't come with a handle, and because it's so large, that's annoying.

This removable printable handle solves the problem. And it gives you an opportunity to add a little color to the drab green mug.

Instructions

I print this in ABS in 4 pieces, each designed to rest on the Kapton-coated heated build plate without using a raft or support.
Print the handle and the OppositeSide on edge. Print the rings with the small openings for the ends of the OppositeSide upward.

Trim off any sharp splots from the initial layer, using a knife.

Use #4 round-head machine screws, about 3/4 inch long or cut longer ones to a maximum of about 22mm long, in the top ring. I press them through the head side (recessed) once first to clean out the hole.

Twist the ring to get access to the threaded side's holes with a 4-40 tap, and tap all the way through.

Assemble the pieces on the mug, tighten the screws, hold the bottom of the handle toward the mug using rubber bands, and weld the pieces with a few drops of acetone (or you can use cyanoacrylate--I've had good luck with Gorilla cyanoacrylate, doesn't harden in the bottle like others). Where the handle touches the top ring, just glue to the threaded end--otherwise you won't be able to remove the handle from the mug.

I printed with about 5% infill for the prototype, and it seems strong enough that I may not do a solid version. I do think I'll seal the surfaces with an acetone vapor bath or a very quick and light brush-on coat of acetone, to prevent drips from getting inside and perhaps allowing mold, or other bad things, to grow.

Handle for Stanley Utility XL Travel Cup 32 oz