How do I turn a half bath into a pantry?

Gut the room and cap off all utilities. You may need a plumber to do this for you. Then wash, prime and paint the walls. Change flooring if you wish. Then decide how you want the shelving and what type. Install brackets and shelves and stock your new space! I would look at lots of shelving options, make space for things like paper towels and toilet paper if purchasing in bulk, space for vases, baking dishes, serving pieces and cookie sheets. Then decide if you want to arrange in sections, like canned goods, baking supplies, pet section, etc. Google and Pinterest have thousands of ideas.

https://www.hgtv.com/remodel/kitchen-remodel/pantry-options-and-ideas-for-efficient-kitchen-storage-pictures

https://www.pinterest.com/TwelveOnMain/home-decor-pantry-ideas/

https://onekindesign.com/2013/10/04/53-mind-blowing-kitchen-pantry-design-ideas/

I would make a plan. Decide what and how you need storage; do you want closed storage or open shelving? Drawers? Are you canned goods or boxes or fresh produce.

Google and Pinterest “kitchen pantry” and print out best photos and take notes.

You can go to a ReStore for gently used cabinets, but I love my slide out drawers in all cabinets which can be installed in older cabinets. Or think about reusing “armoires” or old television cabinets.

Online you can find a number of Virtual Room Design sites that will help you design your space. Make a fresh pony and have fun with this.

I would strongly suggest you keep a sink since you already have plumbing. For vegetables or your dog or just serving as a beer cooler for parties.

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Take out everything that you can and cap off water and sewer lines. Decide your colors for the walls, prime and paint, and install the shelves that work best for you. Adjustable shelves are great to allow for taller and shorter items. Enjoy your new pantry.