How to help my dad who is undergoing chemo, regain some energy?

My dad was diagnosed with stage IV colon cancer about 9 months ago with metastases to the lungs and liver. He completed 12 cycles of chemotherapy and initially had a good response, especially in the liver, so his doctors gave him a planned treatment break. During that break, scans showed progression in the lungs, so he restarted chemotherapy at the end of January 2026 and is currently on his third cycle of this new round. He remains independent (walking, driving, etc.), but he’s been dealing with ongoing fatigue and a fluctuating cough related to the lung metastases. Just this morning he said he's been feeling too weak, and he is tired of taking so much medication.

What are ways we can suggest him to regain his energy back? I think he's having protein, some vitamin supplements, he's drinking water, sleep is not too bad. He has his midday naps but given it is winter, he drives to the mall and does his walks, but apart from that, he doesn't really do much else. I think that since winter, he hasn't gone out much compared to summer.