This is a normal process, as life comes to a gentle end. The body's organs and their functions slowly wind down. He's tired because his 94 yr old heart is in decline, napping because his 94 yr old brain is shrinking. Less responsive.
He's not hungry because his worn out body no longer needs to build new cells; his digestive system will slowly stop processing food.
He might enjoy some very tiny snacks that have quite a strong flavour; a little marmite or gentlemans relish on a finger of buttered bread. A tiny bowl of rhubarb ad custard.
A small glass of his favourite tipple. But don't be disappointed surprised if he's not interested and completely stops eating or drinking. That is normal, natural,.
Keep him comfy. A heated lap blanket. Now, peeing;
Almost all old men develop an enlarged prostate which presses on the bladder, reducing its capacity, so it feels full and needs to empty far more often. (It's not cancer, just old body) Getting up to pee several times at night results. There are ways to manage the frequency of night pee disrupting sleep.
DH is in full remission from prostate cancer and has learned to live with the numerous permanent side effects of his successful treatment; includes reduced bladder capacity . By day he just pees more often. (Bushes, bottles; no blushes) He's found by experimentation that if he drinks no liquids after 7 pm, then a bed time pee leaves bladder empty enough for good unbroken sleep all night long. Wakes up rested.
Some one nearing the end of life, no longer needs to " eat well and drink lots of water to stay healthy" . Their body cells have stopped renewing; their organs are reducing function ready to shut down. That can happen very quickly.
It's time to switch the carers mindset away from " Keeping them alive" to " letting them go gently'
"Staying hydrated" is now less important than a very old man being comfy and safe at night. Then he doesn't worry about pee accidents, can get better sleep,and doesnt risk falling on sleepy /exhausted night trips to bathroom.
See what works; reducing evening liquids; incontinence pants, a bucket or urine bottle beside the bed .
I'm afraid the time is fast approaching when he physically can't carry the responsibility for mum when you're not there. He may already sense that and be struggling with guilt and fear there will be some crisis when they are alone in the house. You're no doubt sharing that same dread. Talk to him.
Can you afford to buy in additional day time visits by a team of carers? Or seek help from Social Services. Their GP should be able to help.
Or, they might need residential respite care.
Do you know any retired nurses, unemployed family members, students on study leave, experienced friends who could move in to dad's home for a few days/ week/ pick up the slack while you sort something out.
If ever there was a time to call in a favour; deploy all your work skillset( organising and communicating).. now is it.