Can I do a one-day trip to Rishikesh from Noida?

Yes absolutely but it will be tight.

• Leave early morning around 5 to 6 am from Noida.
• Take the Vande Bharat or Jan Shatabdi from Delhi to Haridwar which takes 3 to 4 hours.
• From Haridwar go to Rishikesh by taxi which is only 25 km and 45 minutes.
• Spend a few hours in Rishikesh visiting temples, doing yoga, or chilling by the Ganges.
• Have lunch there. By late evening around 7 to 8 pm start heading back by train.

You get roughly 4 to 5 hours in Rishikesh which is enough to see the main attractions and get the vibe. It is doable but exhausting because half the day goes in travel. Better to spend 2 days if you can but one day trip is absolutely possible.