How to Clean Straw & Sippy Cups (and Keep Mold Out of the Valves)
Published October 29, 2026 · Non-Toxic Baby & Screen-Free Play Directory
A simple daily and weekly routine for straw and sippy cups, which parts to check for hidden mold, when to replace them, and which designs are easiest to keep clean.
Straw cups and spill-proof sippy cups are great for toddlers and tough on parents. The same valves, straws and silicone seals that stop spills also trap moisture and milk, which is exactly where mold and gunk like to grow. The fix isn't harsh chemicals; it's taking the cup fully apart every time and letting it dry completely. Here's a routine that keeps cups clean without taking over your evening.
Why Cups Get Moldy
Mold and bacteria need moisture and something to feed on. A spill-proof valve or a narrow straw that never fully dries, especially after milk, smoothies or juice, gives them both. Many parents only discover the problem when they pull out a valve they didn't know came apart. The two biggest causes are not disassembling every part and reassembling before everything is dry.
First: Find Every Part
Before the first use, take the cup completely apart and look at the instructions to see how many pieces it has. Common hidden parts:
- The silicone valve or seal inside the lid.
- The straw and the small weight or valve at the bottom of weighted straws.
- The gasket ring around the lid.
- Spout covers and flip-top hinges.
Take a photo of the parts laid out so everyone in the house knows what "fully apart" looks like.
The Daily Routine (About Two Minutes)
- Empty and rinse right away. Don't let milk or juice sit in a cup in the car or diaper bag. Dump leftovers as soon as you can and rinse with water.
- Take it completely apart: lid, valve, straw, gasket.
- Wash in hot, soapy water using a straw brush through the straw and a small detail brush for valves and lid channels.
- Rinse well.
- Air-dry every part separately on a drying rack, straws standing upright or on a straw drying stand. Don't reassemble until everything is completely dry.
If the manufacturer says the cup is dishwasher-safe, the top rack is usually recommended for lids and silicone parts. A small dishwasher basket keeps valves and straws from falling through. Even with a dishwasher, run a brush through straws now and then, since water doesn't always flush narrow tubes fully.
The Weekly Deep Clean
- Inspect every part with good light. Look into straws, under gaskets and inside valves for dark spots, film or residue.
- Use a deeper method the manufacturer allows. Some cups can be boiled or steam-sterilized; others can't. Check the instructions for your specific cup, since heat can warp some parts.
- Replace the straw brush when its bristles get matted; an old brush can't clean well.
- Store cups apart or with lids off so trapped moisture can escape.
When to Replace Parts
Straws and valves are the parts that wear out first. Replace a part if it has:
- Spots or film that won't clean off.
- A lingering smell after washing.
- Cracks, tears, bite marks or a valve that no longer seals.
- Cloudiness or a sticky texture on silicone.
Many brands sell replacement straws and valves, and some suggest a replacement schedule. Buying spares when you buy the cup means you're never tempted to keep using a worn part. If you find mold in a part your child has been drinking from and you're worried, call your pediatrician for advice.
Which Cups Are Easiest to Keep Clean?
When you're choosing a cup, cleaning should be part of the decision:
- Fewer parts. A cup with three parts gets cleaned properly more often than a cup with seven.
- Removable valves. Valves you can pop out completely are easier to inspect.
- Wide mouths. You should be able to reach the bottom of the cup with a sponge or brush.
- Short, wide straws are easier to brush than long, narrow ones.
- Clear or light-colored parts make residue easy to spot.
- Materials: 18/8 stainless steel and glass bodies are durable and don't hold onto smells; food-grade silicone is soft and easy to wash but should be inspected for wear. See our non-toxic sippy & straw cups guide for options.
- Open cups have nothing to hide mold. Many families use a small open cup at the table and save valved cups for the car or stroller.
Same Idea, Other Gear
The "fully apart, fully dry" rule works for anything with hidden channels: bottle nipples and vents, pouch tops, snack cup lids and squirting bath toys. Bath toys with a hole in the bottom are notorious for mold; our mold-free bath toys guide covers designs that open up or have no holes at all. For plates and bowls, see plastic-free plates & bowls.
A Cup-Cleaning Kit Checklist
- Straw brush set in a couple of sizes.
- Small detail brush for valves and lid channels.
- Drying rack with space for small parts, or a straw drying stand.
- Dishwasher basket for small parts (if your cups are dishwasher-safe).
- Spare straws and valves for the cups you use most.
Frequently Asked Questions
How often should I clean my toddler's straw cup?
After every use: empty it, take every part apart, wash in hot soapy water with a straw brush, and let all the parts air-dry separately before putting it back together.
How do I get mold out of a sippy cup valve?
If you see mold that doesn't clean off easily, the safest choice is to replace that part. Many brands sell replacement valves and straws. If your child drank from it and you're concerned, check with your pediatrician.
Can I put straw cups in the dishwasher?
Only if the manufacturer says the cup is dishwasher-safe. The top rack is usually recommended for lids and silicone parts. It's still a good idea to brush straws by hand from time to time.
How often should I replace sippy cup straws and valves?
Replace them whenever you see spots that won't clean off, a smell that lingers, cracks, tears or bite marks, or a valve that no longer seals. Some brands also suggest a regular replacement schedule.
This article is general information, not medical or safety advice. Always follow the manufacturer's instructions, check CPSC recalls, and ask your pediatrician about your child's specific needs.