Lakshman Jhula, Ram Jhula, Ganga Aarti at both Triveni Ghat and Parmarth Niketan, River Rafting, Ganga Beach, Beetles Ashram. You can also go camping, shopping, and there are beautiful cafes around Lakshman Jhula. Yoga centre if you are into yoga and there are multiple temples too, if you're a religious person.
Mainly Rishikesh is known for its religious sites but if you want some adventure there u must try river rafting , bunjee jumping, camping , trekking and their are also lots of waterfalls some of them are Neer waterfalls, bhatta falls Garud chatti, phool chatti. Garud chatti and Neer water falls are the most famous one because of their natural bath tub.