How do you get tomato stains out of plastic ware?

Sometimes you just don't. Try a soak of white vinegar and baking soda. I only use glass for tomato products just for this reason.

leave the plastic ware in the sun

Take half a lemon dipped in coarse salt and scrub. Should take it out. Or you can use a little bleach then scrub well with water and dish soap, rinse well.

You have my sympathy. Those stains are tough to get off and they make your plastic ware look dirty, no matter how clean they are.

I have tried a paste of baking soda, left on the stain for a few hours, then scrub off. I then follow with baking soda and vinegar. Scrub again after the fizzing stops. I've had mixed results from both.

Try the above suggestions from me and the other hometalkers and see what works.

Then, stick to glass or ceramic for tomato sauce based foods whenever possible.

Good luck

https://foodal.com/knowledge/cleaning/11-ways-remove-stains-plastic/

I've used plain bleach, with water. Make it 1/2 &1/2 of the container size. Good Luck!